Musculoskeletal disorders represent a broad spectrum of conditions that impact the bones, joints, muscles, and connective tissues of the human body. These conditions are frequently characterized by pain and functional limitations, standing as some of the most debilitating and costly health issues in developed nations like the United States. The Social Security Administration (SSA) categorizes musculoskeletal system disorders as those arising from hereditary, congenital, or acquired pathological processes. These impairments can stem from various origins, including infectious, inflammatory, or degenerative processes, traumatic or developmental events, or neoplastic, vascular, or toxic/metabolic diseases. Accurate Musculoskeletal Diagnosis is the cornerstone of effective management and treatment strategies for these diverse conditions.
The SSA has identified three primary categories of musculoskeletal disorders that warrant focused attention: back disorders, osteoarthritis (OA), and other arthropathies. Clinical expertise and a review of medical literature affirm that back disorders and OA are indeed among the most disabling musculoskeletal conditions. Within the category of “other arthropathies,” inflammatory arthropathies are recognized as particularly debilitating conditions that can often be improved with timely and appropriate treatment. While rheumatoid arthritis (RA) and psoriatic arthritis (PsA) are classified as “immune disorders” by the SSA, their most prevalent and often most disabling manifestation is joint inflammation, leading to joint destruction and deformity. Therefore, these conditions are crucial to consider as leading causes of musculoskeletal impairment.
This chapter will delve into specific musculoskeletal conditions that are commonly associated with disability but can often be managed effectively with appropriate treatment, preventing permanent disability for many adults.
TABLE 5-1
Table 5-1: An overview of selected musculoskeletal disorders for diagnostic consideration.
The primary focus of this chapter is on musculoskeletal disorders, beginning with an examination of their epidemiology in the general population. This will be followed by a discussion of overarching issues relevant to these conditions, such as the range of medical professionals involved in care and the settings where diagnosis and treatment typically occur. The chapter will then provide a detailed analysis of chronic low back pain, OA of the hip, knee, and wrist/hand, and inflammatory arthropathies (RA and PsA), addressing key aspects related to their musculoskeletal diagnosis and management.
EPIDEMIOLOGY OF MUSCULOSKELETAL DISORDERS IN THE UNITED STATES
Musculoskeletal disorders are widespread across the United States and are recognized as some of the most disabling and expensive health issues. Disability and work loss due to these disorders are primarily driven by chronic pain and functional impairment. The 2013–2015 National Health Interview Survey (NHIS) estimated that approximately half of all U.S. adults, totaling 126.6 million individuals, live with a musculoskeletal condition. The Global Burden of Disease Study consistently ranks musculoskeletal disorders as leading causes of disability worldwide. In 2016, the top causes of years lived with disability in the U.S. included low back pain (ranked 1st), other musculoskeletal disorders (4th), neck pain (6th), OA (12th), and RA (20th). Accurate musculoskeletal diagnosis is crucial to understanding the prevalence and impact of these conditions.
The economic impact of musculoskeletal disorders is substantial. In 2015, back and neck pain alone accounted for 264 million lost workdays, resulting in $131.8 billion in lost annual earnings. Projections from NHIS data (2010–2012) suggest that by 2040, one in four adults (78 million) will be diagnosed with arthritis. Among these, an estimated 44 percent will report activity limitations attributable to arthritis. Furthermore, individuals with OA experienced $71.3 billion in lost annual earnings, and those with RA lost $7.9 billion. In 2013, there were 62.8 million healthcare visits for low back pain and 6.4 million hospitalizations for arthritis and other rheumatic conditions, highlighting the significant healthcare burden associated with these disorders. The need for precise and timely musculoskeletal diagnosis is underscored by these figures.
CROSS-CUTTING ISSUES FOR MUSCULOSKELETAL DISORDERS
Several common issues are pertinent to all musculoskeletal disorders discussed in this chapter. These include the types of healthcare professionals involved in patient care, the settings where care is provided, and the pervasive issues of pain and limited mobility that often result from these conditions. Effective musculoskeletal diagnosis and management require a multidisciplinary approach.
Medical Professionals Associated with Care
A diverse array of medical professionals contribute to the care of individuals with musculoskeletal disorders. Initial musculoskeletal diagnosis and treatment often occur in primary care settings, with family medicine and general internal medicine physicians providing the majority of care for adults. Physical medicine and rehabilitation physicians also specialize in the musculoskeletal diagnosis and treatment of these conditions. Occupational medicine physicians may be involved when a musculoskeletal disorder is linked to work-related injuries or impairments. Physical medicine and rehabilitation physicians (physiatrists), physical therapists, and occupational therapists are frequently essential in managing patients with functional limitations resulting from musculoskeletal conditions.
For patients suspected of having inflammatory joint, connective tissue diseases, or autoimmune disorders, referral to rheumatologists is common for specialized musculoskeletal diagnosis and treatment, which may include disease-modifying antirheumatic drug therapy. Patients with advanced joint destruction, whether from OA, inflammatory disease, or trauma, are typically referred to orthopedic surgeons for surgical interventions, including joint replacement. In cases of inflammatory arthropathies with extra-articular manifestations, specialists such as pulmonologists (for RA-associated interstitial lung disease) may be consulted.
For patients with disabling chronic pain, multidisciplinary teams may be involved. These teams often include physiatrists or pain physicians (with various medical specializations) collaborating with psychologists, rehabilitation therapists, and other healthcare professionals. Team-based care can also include care managers (often nurses or social workers) or health coaches, facilitating a holistic approach to patient management and emphasizing accurate musculoskeletal diagnosis as the foundation for care planning.
Treatment Settings
Care for musculoskeletal disorders is predominantly delivered in outpatient office-based settings. However, emergency departments and urgent care centers also play a role, particularly for acute injuries or exacerbations. Exercise therapies are commonly administered or supervised by physical therapists, but community and integrative health settings also offer these services. Studies indicate that triaging patients to physical therapists at primary health care centers can improve efficiency and healthcare utilization. Various exercise approaches, such as strength/resistance training, coordination/stabilization exercises, aquatic therapy, cycling, and walking, have proven beneficial for chronic low back pain. Surgical care, when needed, may take place in hospitals or specialized surgical centers. Rehabilitation care can be provided in offices, hospitals (post-surgery), rehabilitation centers, or skilled nursing facilities. The setting for treatment is often determined by the specific musculoskeletal diagnosis and the severity of the condition.
Research on Musculoskeletal Disorders
Despite the high prevalence and public health burden of musculoskeletal conditions, research funding for these disorders is disproportionately low compared to other chronic conditions. In 2012, NIH spending was estimated at $4 per U.S. person affected by chronic pain, compared to $41 for diabetes and $431 for cancer. This funding gap is most pronounced for chronic back pain, the leading cause of disability in the U.S. and globally. NIH tracked back pain as a condition category only starting in 2016, with annual expenditures between $23 million and $30 million (2016–2018), in stark contrast to the billions spent on diabetes and cancer research. This lack of research funding limits our understanding of disease mechanisms, prognosis, and effective treatments for chronic back pain and musculoskeletal disorders in general. Enhanced research, driven by improved musculoskeletal diagnosis and understanding of disease pathways, is crucial for developing more effective therapies.
Standard Measures of Outcome for Musculoskeletal Pain
Pain and functional impairment are the defining features of most musculoskeletal disorders. Consequently, treatment studies commonly utilize patient-reported measures of pain or function as primary outcomes. Although pain and functional outcomes are often correlated, improvements in one do not automatically guarantee improvements in the other. Measures that focus on or include function are particularly relevant. Common patient-reported pain or condition-specific functional measures in musculoskeletal outcomes research include the Brief Pain Inventory Interference scale, the Roland Morris Disability Questionnaire, and the Oswestry Disability Index. These tools are vital for assessing the impact of musculoskeletal diagnosis and treatment interventions.
Treatments for Pain in Musculoskeletal Disorders
Musculoskeletal disorders are the most frequent cause of chronic pain, contributing significantly to the overall burden of these conditions. In 2016, NHIS data revealed that 20.4 percent of U.S. adults (50.0 million) experienced chronic pain, defined as pain on most days in the preceding 6 months. High-impact pain, which limits life or work activities on most days, affected 8 percent (19.6 million). The majority of this pain is attributable to musculoskeletal disorders. Accurate musculoskeletal diagnosis is essential for differentiating pain origins and guiding treatment.
The International Association for the Study of Pain (IASP) and the World Health Organization’s International Classification of Diseases, 11th Revision (ICD-11) classify chronic musculoskeletal pain as persistent or recurrent pain in musculoskeletal structures. The IASP distinguishes between chronic primary musculoskeletal pain (not directly attributed to a known disease) and chronic secondary musculoskeletal pain (arising from an underlying disease). Chronic low back pain is an example of primary musculoskeletal pain, while OA pain and joint pain associated with inflammatory diseases are secondary musculoskeletal pain conditions. This classification system is crucial for precise musculoskeletal diagnosis and tailored treatment approaches.
Numerous pharmacological and non-pharmacological treatments are available for musculoskeletal pain relief. A systematic review of musculoskeletal pain treatment found moderate to strong evidence for the effectiveness of exercise and psychosocial interventions in reducing pain and improving function across various musculoskeletal pain conditions. Pharmacological interventions like oral and topical analgesics and corticosteroid injections (for knee and shoulder pain) showed moderate but less consistent evidence of short-term pain relief. Limited evidence suggests potential benefits from manual therapies, acupuncture, and other treatments.
Guidelines recommend non-drug therapies as first-line treatments for chronic low back pain and OA pain. Medications, especially non-steroidal anti-inflammatory drugs (NSAIDs), are typically recommended as second-line or adjunct therapy. Opioids are no longer recommended for chronic musculoskeletal pain due to limited efficacy compared to other analgesics and significant risks of harm, including addiction and death. Treatment strategies are increasingly focused on comprehensive musculoskeletal diagnosis and multimodal approaches that prioritize non-pharmacological interventions.
CHRONIC LOW BACK PAIN
Chronic back pain is the leading cause of years lived with disability in the United States and results in over 264 million lost workdays annually. In 2013, back pain was the most common reason for healthcare visits among musculoskeletal disorders, with over 57 million physician office visits. Visits for back pain have increased over time, from 11.8 per 100 persons in 1998 to 18.1 per 100 in 2013. Low back pain accounted for most of this increase. Effective musculoskeletal diagnosis of chronic low back pain is crucial for addressing this significant public health issue.
Chronic low back pain is clinically defined as pain persisting in the lower back for at least 3 months. In some individuals, it can progress into a complex condition with persistent anatomical and functional changes in the central nervous system, alongside structural changes in the back. Chronic low back pain can be associated with radicular pain (sciatica) or radiculopathy, indicating spinal nerve root involvement. Lumbar spinal stenosis, common in older adults, presents with characteristic leg or buttock pain during walking.
Radicular pain or radiculopathy is associated with more severe chronic low back pain and poorer functional outcomes. Other factors worsening functional outcomes include co-existing medical and psychiatric conditions and other chronic pain conditions. Over-reliance on biomedical approaches like opioids and spine surgery may also contribute to disability. A thorough musculoskeletal diagnosis must consider these complexities.
Professional Accepted Diagnostic Criteria
Chronic low back pain is diagnosed based on pain location (between the lower rib margin and gluteal folds) and duration (at least 3 months). It is often termed “nonspecific” because a specific cause is rarely identified. The vast majority of cases (over 95 percent in employed populations) lack a definable pathophysiologic abnormality. The IASP and ICD-11 categorize back pain persisting for over 3 months with significant emotional distress or functional impairment as chronic primary pain, unless better explained by another diagnosis (e.g., axial spondyloarthritis, multiple myeloma). Musculoskeletal diagnosis in chronic low back pain often focuses on excluding serious underlying conditions.
Chronic low back pain is multifactorial, involving pathophysiologic, cognitive, emotional, and social elements. Local pain generators in the low back are known, and cognitive/behavioral factors like catastrophizing and activity avoidance play a role. Central nervous system alterations related to pain and emotion processing are also implicated. However, scientific consensus on the relative importance of these factors is limited. Historical diagnoses like psychogenic pain disorder are now obsolete due to scientific advancements. Diagnoses such as sacroiliac joint pain and degenerative disc disease have limited value due to inconsistent diagnostic criteria and usage. Modern musculoskeletal diagnosis emphasizes a comprehensive biopsychosocial assessment.
Routine imaging and laboratory testing are not typically indicated in the initial evaluation of chronic low back pain. Diagnosis is primarily clinical, based on subjective pain experience in a defined anatomical region over time. Imaging and lab tests are used to rule out high-risk sources of back pain, but specific tests for chronic low back pain diagnosis are unavailable. Radiographic abnormalities are common even in pain-free individuals and are not strongly correlated with pain severity or functional impairment. “Abnormal” findings on imaging are considered normal by age 40. Repeated imaging is not useful for evaluating treatment effectiveness or progress. Musculoskeletal diagnosis of chronic low back pain relies heavily on clinical evaluation rather than imaging.
Diagnostic testing is not indicated for most low back pain patients. However, spine X-rays or MRI may be indicated for persistent back pain despite initial treatment. Targeted imaging or lab tests may be needed for patients with trauma, neurologic deficits, “red flag” symptoms, or those considered for surgery. Low back pain is a common symptom, with first episodes often occurring in the second or third decade of life. Approximately 40 percent of children aged 9–18 report back pain. Prevalence is highest in middle-aged adults but remains significant in older age. Back pain is slightly more common in females across all age groups. Among working adults, past-year low back pain prevalence is 26.4 percent, with frequent and severe low back pain at 8.1 percent. Among workers with frequent and severe low back pain, a significant portion report missed workdays and job changes due to back pain. Accurate musculoskeletal diagnosis is crucial for managing this prevalent and impactful condition.
Treatments for Chronic Low Back Pain
Numerous treatments have demonstrated effectiveness in improving function in chronic low back pain. These include exercise therapies, behavioral/psychological therapies, and manual therapies. Multidisciplinary approaches, such as intensive chronic pain rehabilitation programs and primary-care-based collaborative care management interventions, also show functional benefits. Effective treatment strategies rely on accurate musculoskeletal diagnosis to tailor interventions to individual patient needs.
Exercise therapies are recommended as first-line treatments in guidelines for chronic low back pain. Evidence supports various exercise approaches, including strength/resistance, motor control/stabilization, and aerobic exercise, with similar efficacy across techniques. Factors like session number and supervision may enhance improvements. Exercise therapy is associated with a lower likelihood of work disability at approximately 1-year follow-up. Movement-based approaches like yoga and tai chi are also emerging as effective treatments. A comprehensive musculoskeletal diagnosis guides the selection of appropriate exercise modalities.
Psychological or behavioral therapies, such as cognitive behavioral therapy (CBT) and mindfulness-based stress reduction (MBSR), are also considered first-line therapies. CBT interventions show improvements in pain, function, and quality of life. CBT and MBSR have been shown to be superior to usual care in improving functional outcomes. Multidisciplinary rehabilitation, combining exercise, behavioral, and other therapies, is recommended for patients not responding to less intensive interventions and may be particularly relevant for individuals receiving Social Security Insurance and Social Security Disability Insurance. These programs improve function in the short and long term. Musculoskeletal diagnosis informs the integration of psychological and behavioral therapies into comprehensive treatment plans.
Additional conservative therapies like acupuncture, manipulation, and massage may offer modest long-term improvements. Experts suggest combining these with active approaches like exercise for maximized functional outcomes. Interventional therapies (e.g., injections, surgery) generally lack evidence of functional benefits in chronic low back pain, with surgery typically reserved for cases with progressive neurologic deficit or bowel/bladder dysfunction. Medications are generally less beneficial for function than pain in chronic low back pain, with short-term benefits primarily. NSAIDs, duloxetine, tramadol, and opioids may provide small short-term functional improvements. Treatment guidelines emphasize non-drug therapies as first-line options, with medications as second-line or adjuncts. Opioids are no longer recommended for chronic musculoskeletal pain due to risks and lack of superior efficacy. Effective management of chronic low back pain requires a holistic approach grounded in accurate musculoskeletal diagnosis.
Length of Time to Improvement for Chronic Low Back Pain
Evidence regarding the likelihood of achieving a point where low back pain is no longer disabling or the time required is limited. The efficacy of chronic back pain treatments does not appear to differ by age. Prognosis and treatment planning are integral aspects of musculoskeletal diagnosis.
OSTEOARTHRITIS
Osteoarthritis (OA) encompasses a group of degenerative joint disorders characterized by clinical and radiographic findings. It is the most common form of arthritis, affecting over 30 million Americans. OA is not just “wear and tear” but a complex interplay of genetic, metabolic, biomechanical, and biochemical joint changes affecting the entire joint and surrounding tissues. OA is becoming the leading cause of disability for middle-aged and older Americans, with age being a strong risk factor. Women are more prone to OA, and their condition tends to be more severe. Accurate musculoskeletal diagnosis of OA is crucial for effective management and mitigating disability.
OA progressively damages synovial joint structure, particularly articular cartilage. It can affect any synovial joint and occurs across all populations. There is no known cure or method to reverse OA. Therapy aims to reduce joint pain and improve function using both pharmacological and non-pharmacological interventions. Pharmacological therapy often starts with analgesics, topical analgesics, and NSAIDs, prescribed by primary care physicians or physiatrists. Intra-articular corticosteroid injections can provide temporary pain relief but should be used sparingly. Non-pharmacological therapy includes patient education, weight loss (if needed), physical therapy (PT) for joint mobility and muscle strengthening, low-impact exercise, and assistive devices. Total joint replacement may be considered in severe cases. Healthcare settings for OA management include physician offices, PT centers, hospitals, and rehabilitation centers. The choice of treatment is guided by the specific musculoskeletal diagnosis and disease stage.
The primary symptom of OA is joint pain that worsens with activity and improves with rest. Articular cartilage degeneration is the hallmark of OA, driven by stress, injury, mechanical overload, and aging. Joint injury increases OA risk, but most cases occur without a specific injury history. OA leads to progressive articular cartilage damage, resulting in pain and impaired joint function. Joint shape may become distorted over time, with bone spurs developing. Bone or cartilage fragments can cause further pain and damage within the joint space. Unlike inflammatory arthropathies, OA affects only joints, not internal organs. OA is more common in older people; before age 45, men are more affected, while after 45, women are more affected. Symptomatic knee OA prevalence increases with age, peaking between 55 and 64 years. OA can cause pain, stiffness, swelling, reduced function, and disability, impacting daily tasks and work. Progressive joint deformity, contractures, and swelling can also occur. A timely and accurate musculoskeletal diagnosis is essential to manage OA progression.
Primary or idiopathic OA can be localized (single joint) or generalized (three or more joints). Obesity is a risk factor for knee OA and, to a lesser extent, hip and hand OA. Women have a higher risk of knee OA than men. Joint dysplasia, laxity, neuropathies, metabolic disorders, and genetic predisposition can also increase OA risk, as can sustained physically demanding activities. Specific OA symptoms include pain, stiffness, reduced movement, and joint swelling, typically exacerbated by activity and relieved by rest. Joint tenderness and crepitus may be present, without systemic symptoms. Early OA may be painless, but advanced disease can involve grinding, locking, buckling, and instability. Advanced OA is painful, and muscle overuse can lead to pain syndromes in other musculoskeletal areas. Functional limitation severity depends on the affected joint and the individual’s activities. Hip and knee OA impair mobility, locomotion, and daily living activities. Hand OA limits vocational, recreational, and self-care activities. Patients may struggle with computer use, lifting, and eventually, daily living tasks. Comprehensive musculoskeletal diagnosis is critical to assess the functional impact of OA.
Professional Accepted Diagnostic Criteria for Osteoarthritis
No single test definitively diagnoses OA. Doctors use multiple methods for musculoskeletal diagnosis to confirm OA and rule out other conditions. Family physicians or internists typically start by taking a medical history and conducting a physical exam to assess symptoms and rule out co-occurring disorders. Specific tests may include:
- Physical exam: to assess general health, reflexes, and problem joints.
- X-rays: to detect cartilage loss, bone damage, and bone spurs, although early damage may not be visible.
- MRI: to visualize damage to joint tissues, especially articular cartilage, menisci, and subchondral bone.
- Blood tests: to exclude other causes of symptoms.
- Joint fluid samples: to check for infection or gout.
OA can be defined pathologically, radiographically, or clinically. Radiographic OA has long been the reference standard, although radiographic OA may exist without clinical OA. Musculoskeletal diagnosis often involves a combination of clinical, radiographic, and sometimes pathological assessments.
General Treatments for Osteoarthritis
Numerous pharmacological and non-pharmacological therapies offer temporary relief from OA pain. Initial treatment should combine both approaches, although no pharmacological interventions can cure or alter OA progression. Effective treatment planning hinges on accurate musculoskeletal diagnosis. Possible treatments include:
- Analgesics: ranging from mild over-the-counter to strong prescription medications. Oral acetaminophen is a first-line recommendation for hip and knee OA.
- Topical products: ointments, gels, sprays, and creams applied directly to the skin. Topical NSAIDs are more effective than placebo for OA.
- NSAIDs: oral or topical, for temporary pain relief by blocking inflammatory enzymes. Side effects include stomach pain, nausea, diarrhea, and ulcers. NSAIDs can interact with other medications.
- Anti-neuropathic pain medications: acting on the nervous system to reduce nerve pain (e.g., gabapentin, serotonin-norepinephrine reuptake inhibitors).
- Corticosteroids: rapidly reduce inflammation, oral or injected, but long-term use has side effects.
This discussion focuses on OA affecting weight-bearing joints (hips and knees) and non-weight-bearing joints (hands and wrists), the most commonly affected sites. OA treatment goals are pain reduction and functional improvement, as there is no cure. Patient response varies based on affected joints and disease stage (mild, moderate, severe). OA progression rate varies among patients and joints. Despite numerous treatments, progressive knee OA can lead to reduced mobility and systemic complications. Initial pain relief treatments include acetaminophen, followed by oral and topical NSAIDs. Orthotics and footwear modifications can be helpful, but are patient-specific. Exercise programs are crucial for knee OA to maintain function. Intra-articular corticosteroid injections can reduce local inflammation and improve symptoms for a limited duration. Acupuncture is recommended for chronic moderate to severe OA when surgery is not feasible. Platelet-rich plasma shows promise for symptomatic relief in early knee OA, but more research is needed. A stepped-care approach can optimize non-surgical OA treatment, but studies show no significant differences in pain and function over 2 years compared to regular care. Treatment strategies are guided by the musculoskeletal diagnosis and individual patient profiles.
Knee and Hip Osteoarthritis
Symptomatic knee OA prevalence increases with age, peaking between 55 and 64 years. Globally, prevalence is about 3.8 percent, higher in women (4.8 percent) than men (2.8 percent). Knee OA is the most common lower extremity OA site, affecting medial, patellofemoral, or lateral compartments. OA affects all joint structures, characterized by articular cartilage loss, subchondral bone sclerosis, and osteophyte formation, leading to pain and impaired function, sometimes deformity and contracture. Women are more likely to develop knee OA, especially after age 50. Hip OA is less common than knee or hand OA but is the most prevalent hip pathology. Hip OA rates increase with age, with no gender difference. Occupational heavy lifting and stair climbing increase hip OA risk. Precise musculoskeletal diagnosis is essential for managing knee and hip OA effectively.
Professionally Accepted Diagnostic Criteria
Musculoskeletal diagnosis of hip and knee OA is typically based on patient history, physical examination, and plain radiographs. Laboratory tests are usually normal. Joint pain is the primary symptom, often accompanied by decreased range of motion, crepitus, and sometimes joint deformity. Knee pain severity is a stronger predictor of functional impairment than radiographic severity. Radiographic hallmarks of OA include decreased joint space (due to cartilage erosion), osteophytes, and subchondral bone changes like sclerosis and cysts. Groin pain is classic for hip OA, with other symptoms including buttock pain, hip pain, stiffness, and functional limitations. Hip OA onset can be insidious, worsening with weight-bearing activity and improving with rest, but advanced hip OA can be painful even at rest. Radiography is the primary diagnostic study for hip OA; MRI and ultrasound are typically not necessary, except in complex cases.
Treatments Demonstrated to Improve Hip and Knee Function
Exercise is the cornerstone of non-pharmacological treatment for knee OA, focusing on lower extremity stretching, aerobic conditioning, and balance exercises. Treatments for knee and hip OA are similar, with activity modification being helpful to avoid pain-exacerbating activities. Non-pharmacological therapy often begins with exercise. Strong evidence supports PT to improve function and reduce pain in mild to moderate hip OA. Exercise for knee and hip OA reduces pain, improves physical function, and self-efficacy, with small benefits for depression. Supervised home-based exercise shows significant improvements in arthritis symptoms. Exercise programs should be tailored to individual ability and preference. Braces or splints can benefit patients with OA of the first metacarpal or wrist joint. Obese patients undergoing total hip arthroplasty may have lower absolute outcome scores but report similar satisfaction and relative improvement in pain and function compared to non-obese patients. Musculoskeletal diagnosis guides the selection of appropriate treatments and rehabilitation strategies.
Knee replacement (total or partial) is performed to restore function and relieve pain in severely damaged knees. While effective, postoperative complications include blood clots, wound issues, infection, and prosthetic component problems. Studies show that about 40 percent of patients who had knee replacements returned to work. Hip replacement is also common, with about 33 percent returning to work one year post-surgery. Age is a significant predictor of return to work after joint replacement, with lower rates in older patients. Return to work time after hip arthroplasty varies widely. Joint arthroplasty is considered for severe OA cases. While joint replacements can relieve pain and improve function, postoperative work experience varies based on pre-operative factors and job demands. Progressive knee OA can lead to reduced mobility and systemic complications. Complications can arise from medications, injections, surgery, and arthroscopy. Surgery is generally a last resort. Pre-operative and postoperative PT can improve outcomes after total hip arthroplasty. Post-operative PT improves early function more than no PT. Exercise programs can improve physical function, depression, and pain in knee and hip OA. Comprehensive musculoskeletal diagnosis and pre- and post-operative care are crucial for optimizing outcomes.
Length of Time to Improvement
Time to improvement varies greatly, depending on comorbidities, surgical complexity, and patient pre-surgical condition. Pre-operative preparation and post-operative therapy can improve results. Age does not appear to strongly influence improvement after hip and knee replacement. Realistic expectations regarding recovery timelines are an important part of musculoskeletal diagnosis and patient education.
Hand and Wrist Osteoarthritis
Hand OA is the most common form of arthritis, associated with aging. Estimates reach 78 percent in men and 99 percent in women over 65. Symptoms include pain, stiffness, functional limitation, and reduced grip strength, but gradual onset allows adaptation, and disability complaints are less common than with other OA types. Wrist OA involves painful degeneration of wrist joint articular surfaces. Symptoms include pain, swelling, stiffness, and crepitation. Secondary wrist OA, often from post-traumatic conditions, is most common. Accurate musculoskeletal diagnosis is vital for managing hand and wrist OA.
Professionally Accepted Diagnostic Criteria
Hand OA commonly affects the first carpometacarpal joint (thumb base), distal interphalangeal joints (finger tips), and proximal interphalangeal joints (middle finger joints). It is characterized by articular cartilage loss, subchondral bone sclerosis, and osteophyte formation, leading to pain, impaired function, and sometimes deformity/contracture. Musculoskeletal diagnosis is typically based on patient history, physical exam, and radiographs. Radiographic evidence is highly reliable for hand OA evaluation. Pain, stiffness, and disability are weakly to moderately associated with radiographic findings.
Wrist OA often presents with pain as the primary symptom. Physical examination includes upper limb inspection; motion loss is a common finding. Additional imaging is usually unnecessary for musculoskeletal diagnosis. Motion loss is the primary limitation in wrist arthritis, impacting daily living activities. Advanced wrist OA results in severe pain and motion limitations, impairing daily living.
Treatments Demonstrated to Improve Function in Patients with Hand and Wrist Osteoporosis
Evidence suggests occupational therapy may benefit hand and wrist OA patients. Oral acetaminophen and NSAIDs can relieve symptoms, as can ice, heat, and topical creams. Intra-articular corticosteroid or hyaluronate injections offer inconsistent temporary relief. Common treatments include splinting and joint arthroplasty for thumb carpometacarpal joint OA; splinting, corticosteroid injections, fusion, and arthroplasty for wrist OA; and joint fusion for finger joint OA. Surgery generally provides predictable pain relief but may reduce function. Joint arthroplasty can decrease pain in severe thumb carpometacarpal joint OA, and joint fusions can reduce pain and improve function in severe wrist and finger joint OA. Treatment strategies for hand and wrist OA are guided by musculoskeletal diagnosis and functional needs.
Length of Time to Improvement
Improvement time varies based on patient factors, pre-operative condition, and post-operative therapy. Most patients achieve near-maximum surgical benefit within 6 months. Age is not a strong determinant of outcomes in hand and wrist OA treatment. Comorbidities like muscle weakness, neurologic disorders, and diabetes can negatively influence outcomes. Pre-operative preparation and post-operative therapy can improve results, with therapy type and duration determined by physician judgment and patient condition. Realistic expectations regarding recovery timelines are an important part of musculoskeletal diagnosis and patient education.
INFLAMMATORY ARTHROPATHIES
Inflammatory arthropathies are conditions characterized by joint and often other tissue inflammation. They include rheumatoid arthritis (RA), psoriatic arthritis (PsA), ankylosing spondylitis, juvenile idiopathic arthritis, and systemic lupus erythematosus, among others. RA and PsA are common inflammatory arthropathies and significant causes of adult disability. Accurate musculoskeletal diagnosis is crucial for early intervention and management of these conditions.
Rheumatoid Arthritis
Rheumatoid arthritis (RA) is a chronic autoimmune disease causing pain, aching, stiffness, and swelling in multiple synovial joints. It typically affects small joints of the hands and feet symmetrically but can affect any synovial joint. RA is a systemic disease, potentially affecting other organ systems like the heart, lungs, and eyes, and causing systemic symptoms like fatigue, fever, and weight loss. Musculoskeletal impairments are the most disabling aspect of RA and the major source of functional limitations. The underlying pathophysiology is synovium inflammation. Disease flares worsen joint pain and swelling. Persistent inflammation leads to cartilage and bone erosion, joint destruction, and deformities, causing chronic pain and functional limitations. Early and precise musculoskeletal diagnosis of RA is critical to prevent irreversible joint damage.
Professionally Accepted Diagnostic Criteria for Rheumatoid Arthritis
Musculoskeletal diagnosis of RA is based on clinical history, physical examination, and laboratory findings. The 2010 American College of Rheumatology (ACR)/European League Against Rheumatism (EULAR) classification criteria are the generally accepted diagnostic criteria, developed for research studies to identify early-stage RA. These criteria are applied when there is clinical suspicion of RA based on definite synovitis in at least one joint, not better explained by another condition. A score of at least 6 out of 10 indicates “definite RA.” The criteria are designed for recent-onset and active RA; longstanding or inactive RA may be diagnosed based on prior history meeting these criteria. Seronegative RA patients lacking rheumatoid factor and anti-citrullinated protein antibody may still be diagnosed if clinical findings are characteristic and alternative diagnoses are excluded. Radiographic findings of bone erosions can support the diagnosis, but radiography is generally not required.
TABLE 5-6
Table 5-6: Diagnostic criteria for rheumatoid arthritis in musculoskeletal diagnosis.
Lifetime RA risk is two to three times higher in women than men. Onset peaks between 30 and 50 years but can occur at any age. Risk factors include older age, family history of RA, and smoking. Early and accurate musculoskeletal diagnosis is crucial for initiating timely treatment and improving long-term outcomes.
Standard Measures of Outcomes for Rheumatoid Arthritis
Principal outcome measures for RA treatment response and remission are composite, multidimensional, incorporating clinical data, functional assessment, patient-reported symptoms, and global assessment. Routine physical function assessment is strongly recommended in RA treatment strategies. These measures are widely used in research but variably applied in routine U.S. clinical practice. Standardized outcome measures enhance the precision of musculoskeletal diagnosis and treatment monitoring.
ACR20: The ACR defines therapy response with ACR20, ACR50, and ACR70, indicating 20 percent, 50 percent, or 70 percent improvement on core outcome measures. These include swollen joint count, tender joint count, pain visual analog scale, patient global assessment, physician global assessment, inflammatory marker levels (ESR or CRP), and physical functioning (HAQ). ACR20 is most widely used, recommended by the FDA for new RA drug studies, and common as a primary outcome in clinical trials. However, other disease activity scales are considered more feasible for clinical practice monitoring.
Disease activity scales: ACR-endorsed instruments measure RA disease activity and remission, including PAS, PASII, RAPID3, CDAI, DAS, and SDAI. All are multidimensional, composite measures from physical exam, lab markers, functional measures, pain symptoms, and global assessments. They are sensitive in distinguishing disease activity levels and are commonly reported as secondary outcomes in drug trials and recommended for routine clinical assessments. Disease activity scores correlate closely with RA functional impairment. However, functional impairment can persist even with quiescent disease due to prior joint damage. Functional assessment is crucial in musculoskeletal diagnosis and outcome evaluation.
Functional assessment: The Health Assessment Questionnaire (HAQ) is the most widely used measure of functional capacity in RA, assessing activities of daily living over the past week. It can be self-administered or clinician-administered and is a common secondary outcome in RA drug trials. HAQ is a strong predictor of work disability, though it does not explicitly assess work activities. Other instruments specifically measuring work-related functioning include the Work Productivity and Activity Impairment Questionnaire, Work Instability Scale, and Work Productivity Survey, but these are not yet widely used.
Treatments for Rheumatoid Arthritis
RA treatment goals include reducing symptoms, preventing deformity, maintaining quality of life, and limiting extra-articular manifestations. Disease-modifying antirheumatic drugs (DMARDs) are the mainstay of therapy, limiting joint damage and improving function. Rheumatologist care is associated with earlier DMARD initiation and improved treatment response, leading to less joint destruction, lower functional impairment, and reduced need for surgery. Traditional DMARDs include methotrexate, leflunomide, hydroxychloroquine, and sulfasalazine. Biologic DMARDs include anti-TNF agents and non-TNF biologics. Janus kinase (JAK)-inhibitors, like tofacitinib, are another DMARD class. Medications for short-term symptom relief include NSAIDs and steroids. Non-pharmacological treatments include physical and occupational therapy, exercise, patient education, and psychosocial interventions. Pain management addresses both underlying disease and pain symptoms. Surgery is indicated for intractable pain, severe motion loss, or functional impairment despite medical management. Effective RA management depends on accurate and timely musculoskeletal diagnosis and comprehensive treatment strategies.
TABLE 5-7
Table 5-7: Medications used to treat rheumatoid arthritis in musculoskeletal diagnosis and management.
Evidence-based guidelines for established RA pharmacologic management include ACR and EULAR guidelines. Therapy is recommended for patients not in remission with any disease activity. Early therapy initiation is associated with better outcomes. Specific agent selection depends on disease activity, prior treatments, response, toxicities, and comorbidities. The goal is sustained remission or low disease activity. ACR guidelines recommend traditional DMARD monotherapy (methotrexate preferred) as first-line treatment. For insufficient response, combination DMARDs, biologic DMARDs, or tofacitinib are recommended. For persistent moderate to high disease activity on anti-TNF therapy, adding traditional DMARDs is recommended. If treatment targets are not met with a biologic DMARD, switching to a different biologic DMARD is advised. Short-term glucocorticoids may be added for persistent moderate/high disease activity or flares. Once low disease activity is achieved, regimen continuation is recommended due to relapse risk. DMARD tapering can be considered in remission but discontinuing all therapy is generally discouraged due to high relapse risk. EULAR recommendations are largely similar to ACR guidelines. Both emphasize early and aggressive treatment informed by musculoskeletal diagnosis.
ACR and EULAR guidelines have limitations, not discussing non-pharmacologic treatments or optimal combinations. RCTs support exercise for muscle strength and quality of life, while complementary therapies show no benefit. Newer therapies like sarilumab and baricitinib have emerged since guideline publication. Neither guideline explicitly discusses DMARD impact on work-related functional capacity, the outcome of principal interest for disability assessment. RA treatment literature broadly lacks evidence guiding refractory RA management. Refractory RA, unresponsive to multiple DMARDs, is difficult to treat, and prevalence in SSA beneficiaries is likely higher. Baracitinib shows promise for refractory RA. Novel therapies are under investigation. Pharmacologic RA treatments can improve symptoms but have toxicities, limiting use in some patients. Few studies rigorously assess RA treatment impact on work outcomes directly. Indirect evidence from HAQ scores suggests functional improvement with various DMARDs. However, most studies don’t focus on severe or refractory RA patients, making it unclear if these therapies meaningfully improve work-related function in the SSA population. Studies evaluating treatments in patients unresponsive to at least one biologic DMARD are more relevant. Sarilumab, filgotinib, baricitinib, and tofacitinib have shown HAQ score improvements in anti-TNF-inadequate responders. Secukinumab did not show HAQ improvement in this population. Further research is needed to assess the impact of RA treatments on work outcomes, particularly in populations with severe or refractory disease, and to refine musculoskeletal diagnosis for better treatment stratification.
Length of Time to Improvement for Rheumatoid Arthritis
NSAIDs and low-dose glucocorticoids can provide symptom relief within days. DMARDs typically show clinical improvement within 3 months, though some patients may take 3–6 months. Clinical trials assess treatment response at 3 and 6 months. EULAR guidelines recommend therapy change if no improvement is seen after 3–6 months. Timely and accurate musculoskeletal diagnosis is critical for initiating treatment and monitoring response within these timeframes.
Psoriatic Arthritis
Psoriatic arthritis (PsA) is a chronic inflammatory disease of joints, spine, and entheses. It may affect other tissues and is commonly associated with psoriasis. Skin manifestations usually precede arthritis, but they can present simultaneously, or arthritis may present first in some cases. PsA is heterogeneous, with five recognized subtypes: mono- or oligo-arthritis, polyarthritis, distal-interphalangeal-joint predominant disease, psoriatic spondylitis/sacroiliitis, and arthritis mutilans. Peripheral oligoarticular or polyarticular disease is most common; arthritis mutilans is rarer and more severe. Comprehensive musculoskeletal diagnosis is essential due to the varied presentations of PsA.
Professionally Accepted Diagnostic Criteria for Psoriatic Arthritis
Musculoskeletal diagnosis of PsA is based on clinical history, physical examination, laboratory findings, and radiography. The Classification of Psoriatic Arthritis (CASPAR) criteria are the most widely used diagnostic and classification criteria, highly sensitive and specific. These criteria are applied when inflammatory disease of joints, spine, or entheses is suspected. A score of at least 3 points indicates PsA. Laboratory markers are less helpful in confirming PsA than in excluding other inflammatory arthropathies.
TABLE 5-8
Table 5-8: Classification criteria for psoriatic arthritis in musculoskeletal diagnosis.
PsA affects men and women equally. Average diagnosis age is 40–50. Obesity is a risk factor for PsA development. Early and accurate musculoskeletal diagnosis is critical for effective PsA management.
Standard Measures of Outcomes for Psoriatic Arthritis
Similar to RA, PsA’s heterogeneous manifestations require composite, multidimensional outcome measures for treatment response assessment. Principal measures incorporate clinical data, functional assessment, patient-reported symptoms, and global assessment. These measures are primarily for research and clinical trials, and their routine use by U.S. rheumatologists is unclear. Standardized outcome measures improve the precision of musculoskeletal diagnosis and treatment monitoring.
Treatment response criteria for PsA: ACR20 is frequently used in PsA drug trials. PsA-specific criteria include Psoriatic Arthritis Response Criteria (PsARC) and Minimal Disease Activity (MDA) criteria. PsARC defines response as achieving two of: tender/swollen joint count improvement by ≥30 percent, patient global improvement, or physician global improvement. MDA criteria are met when low scores are achieved in five of seven domains: tender joint count, swollen joint count, psoriasis body surface area, pain symptoms, patient global activity, HAQ, and tender entheseal points.
Disease activity scales: RA disease activity measures like DAS have been used in PsA trials, but RA-specific measures may be less accurate for PsA due to clinical presentation differences. PsA-specific disease activity measures include Disease Activity Index for Psoriatic Arthritis, Psoriatic Arthritis Joint Activity Index, Composite Psoriatic Disease Activity Index, and Psoriatic Arthritis Disease Activity Score. All are composite measures from physical exam, lab markers, pain symptoms, global assessments, functional measures, and quality of life. PsA disease activity scores correlate closely with functional impairment. Functional impairment can persist even with quiescent disease due to prior joint damage. Functional assessment is crucial in musculoskeletal diagnosis and outcome evaluation.
Functional assessment: HAQ, developed for RA, is also commonly used in PsA clinical trials.
Treatments for Psoriatic Arthritis
PsA treatment goals are symptom control, structural damage prevention, and improving function and quality of life. DMARDs are the mainstay of treatment, limiting joint damage and prescribed by rheumatologists. There is considerable overlap in DMARDs for PsA and RA, but also some differences in drug classes. Traditional DMARDs for PsA are oral; IL-12/23 and IL-17 inhibitors are subcutaneous injections. NSAIDs and glucocorticoids offer short-term symptom relief. Non-pharmacologic treatment options are similar to RA. Pain management is crucial, with adjunctive therapies for pain symptoms. Surgical indications are similar to RA. Effective PsA management hinges on precise musculoskeletal diagnosis and tailored treatment strategies.
TABLE 5-9
Table 5-9: Medications used to treat psoriatic arthritis in musculoskeletal diagnosis and management.
Evidence-based guidelines for PsA pharmacologic management include ACR/NPF guideline, EULAR recommendations, and GRAPPA recommendations. Treatment goal is remission or minimal/low disease activity. Preferred treatment depends on disease severity, medication toxicities, comorbidities, and specific PsA manifestations. Evidence base for PsA guidelines is more limited than for RA guidelines, and guidelines differ. ACR/NPF guideline prefers anti-TNF biologics, traditional DMARDs, IL-17 inhibitors, and IL-12/23 inhibitors as initial treatments. For less active disease, NSAIDs can be considered. For inadequate response, subsequent options are anti-TNF biologics, IL-17 inhibitors, IL-12/23 inhibitors, and abatacept or tofacitinib. Switching to a different anti-TNF DMARD is preferred over other biologics after anti-TNF failure. For traditional DMARD non-responders, apremilast addition or switching to a new traditional DMARD is considered. For active PsA with psoriatic spondylitis, anti-TNF DMARDs are preferred, followed by IL-17 inhibitors. For enthesitis-predominant PsA, NSAIDs, anti-TNF DMARDs, and tofacitinib are preferred over traditional DMARDs. EULAR recommendations prefer traditional DMARDs as first-line therapy over biologics. For mild disease, NSAIDs and intra-articular glucocorticoids are acceptable initial therapy; for more severe disease or unfavorable prognostic factors, traditional DMARDs (methotrexate preferred) are recommended. EULAR guidelines do not favor IL-17 over IL-12/23 inhibitors and do not address abatacept or tofacitinib. GRAPPA recommendations are similar to EULAR for peripheral arthritis, axial disease, and enthesitis management. PsA treatment guidelines, while based on evidence and expert opinion, have limitations, especially regarding work-related functional capacity. PsA treatment literature lacks guidance for severe or treatment-resistant disease management. Ixekizumab, ustekinumab, and secukinumab show efficacy in anti-TNF-inadequate responders. Novel therapies are under investigation. PsA pharmacologic treatments overlap with RA treatments, as do toxicities. Musculoskeletal diagnosis guides the selection of appropriate therapies based on disease characteristics and severity.
Few studies rigorously assess PsA treatment impact on work outcomes. Certolizumab reduces absenteeism and presenteeism. Infliximab improves work productivity but not employment status. Indirect evidence from HAQ scores shows clinical improvements with various biologic DMARDs. However, most studies do not focus on severe or refractory PsA, limiting understanding of work-related functional capacity improvement in the SSA population. Studies evaluating treatments in patients unresponsive to at least one biologic DMARD are more relevant. Tofacitinib improves HAQ scores in anti-TNF-inadequate responders. Ustekinumab did not achieve clinically meaningful functional improvement in this population. Further research is needed to assess PsA treatment impact on work outcomes, particularly in severe/refractory disease, and to refine musculoskeletal diagnosis for tailored treatment approaches.
Length of Time to Improvement for Psoriatic Arthritis
Similar to RA, NSAIDs and low-dose glucocorticoids offer rapid symptom relief for PsA. DMARDs typically show clinical improvement within 3 months, but some patients may take 3–6 months. Clinical trials assess response at 3 and 6 months. EULAR guidelines recommend therapy change if no improvement is seen after 3–6 months. Prompt and accurate musculoskeletal diagnosis is essential for timely treatment initiation and monitoring of response within these timelines.
NEW AND DEVELOPING TREATMENTS FOR MUSCULOSKELETAL DISORDERS
Biologics are increasingly used in orthopedics as adjuvants for musculoskeletal injury healing. Improved outcomes with biologics combined with standard therapies have spurred further clinical interest. Biologics show some benefit in improving function, pain scores, and healing time in foot and ankle traumatic injuries. JAK-inhibitors are gaining attention for potential utility in immune-mediated diseases, but limitations exist regarding selectivity, routes, and dosing. Advancements in musculoskeletal diagnosis and understanding of disease mechanisms are driving the development of novel therapies.
Advanced drug delivery strategies for musculoskeletal disorders involve therapeutic drugs, novel delivery vehicles, and innovative delivery approaches. These strategies target bone, cartilage, tendons, ligaments, and skeletal muscles. Bioactive factor use in cartilage injury management is progressing, with innovative biologic and engineering strategies enhancing efficacy. Techniques in material synthesis, polymer modification, carrier development, and scaffold fabrication enable treatment delivery to the joint environment. Nanotechnology and nanomaterials improve drug retention in the joint space. Tissue engineering and regenerative approaches for articular cartilage injuries, particularly cartilage regeneration technology, hold potential for repairing and preventing debilitating knee OA progression. Three-dimensional bioprinting techniques are useful for fabricating scaffolds for biomedical and regenerative medicine, enabling creation of bones, vascular, skin, cartilage, and neural structures. Regenerative rehabilitation integrates biologic and bioengineering advances, particularly stem cell therapy for tissue repair and regeneration. Stem cells and stromal cells stimulate musculoskeletal tissue. Delivery strategies are improving cell viability and retention. These emerging treatments hold promise for improving outcomes in musculoskeletal disorders, complementing advancements in musculoskeletal diagnosis.
SUMMARY AND CONCLUSIONS
Musculoskeletal disorders are diverse conditions affecting bones, joints, muscles, and connective tissues, causing pain and functional loss, and are among the most disabling and costly conditions in the United States. Chronic pain and functional loss are the primary mechanisms leading to disability and work loss. Accurate and timely musculoskeletal diagnosis is the foundation for effective management and treatment.
SSA identified back disorders, OA, and other arthropathies as key musculoskeletal disorder categories. These encompass the most disabling conditions. RA and PsA, though classified as immune disorders, are also considered leading causes of musculoskeletal impairment due to joint inflammation and destruction.
Chronic low back pain, a primary musculoskeletal pain condition defined by pain lasting over 3 months, is highly prevalent and the top cause of years lived with disability. Radicular pain or radiculopathy worsens severity and functional outcomes. Overuse of biomedical approaches like opioids and surgery can contribute to disability. Effective treatments include exercise, behavioral/psychological, and manual therapies, and multidisciplinary approaches. Medications are less beneficial for function than pain in chronic low back pain, with short-term benefits primarily. Musculoskeletal diagnosis guides treatment strategies for chronic low back pain, focusing on function improvement.
OA, a progressive synovial joint destruction disease without a cure, causes chronic pain and stiffness and can be disabling. It is most common in older people, with gender differences varying by age. Progressive OA can lead to reduced mobility and systemic complications. Exercise therapy and psychosocial interventions are effective for pain relief and function improvement in OA. Joint arthroplasties and fusions can relieve pain and improve function but carry risks and should be considered after non-surgical approaches fail. Musculoskeletal diagnosis informs OA management, emphasizing function maintenance and pain relief.
Inflammatory arthropathies, including RA and PsA, are characterized by joint and tissue inflammation, causing significant adult disability. RA and PsA are systemic inflammatory diseases with joint inflammation and destruction as prominent clinical manifestations, causing work-related functional impairment. Effective treatments for RA and PsA exist, with expanding options including newer biologic agents. Physical functioning is commonly assessed in RA and PsA therapy trials, providing more evidence on treatment impacts on function than for many other disabling conditions. Early and precise musculoskeletal diagnosis is crucial for initiating effective treatments for inflammatory arthropathies.
Many pharmacologic treatments for RA and PsA improve physical functioning, including biologic DMARDs for more severe disease. However, the extent of work-related functional capacity improvement in individuals with severe impairments qualifying for SSA programs remains uncertain. Clinical trials often don’t focus on severely impaired individuals, and treatment response may be more modest in refractory disease. Irreversible joint damage in RA and PsA can limit functional improvement from medical management alone. Early diagnosis and treatment to prevent joint destruction are critical. Evidence directly linking specific RA and PsA therapies to work outcomes is limited, though HAQ scores correlate with work disability. Future research should focus on work outcomes and severe/refractory disease populations to optimize musculoskeletal diagnosis and treatment strategies for improved functional capacity and reduced disability.
REFERENCES
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Footnotes
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