Bursitis, characterized by the inflammation of a bursa, a synovial fluid-filled sac that cushions joints, is a common musculoskeletal complaint. These bursae are located throughout the body, adjacent to bony prominences and between soft tissues like muscles, tendons, and ligaments, facilitating smooth movement. While bursitis is frequently diagnosed, it is crucial for clinicians to consider a broad differential diagnosis to ensure accurate management and optimal patient outcomes. This article provides an in-depth exploration of the differential diagnosis of bursitis, enhancing the understanding of this condition for healthcare professionals.
Etiology and Pathophysiology of Bursitis
Understanding the diverse etiologies of bursitis is fundamental to differential diagnosis. Bursitis arises from various factors, broadly categorized as:
- Overuse and Repetitive Stress: Repeated motions or sustained pressure are common culprits. Examples include prolonged kneeling (“housemaid’s knee” or prepatellar bursitis) or leaning on elbows (“student’s elbow” or olecranon bursitis).
- Trauma: Direct blows or injuries can lead to bursal inflammation. Traumatic bursitis also increases the risk of septic bursitis due to potential skin penetration.
- Infection: Septic bursitis, often caused by Staphylococcus aureus, can result from direct inoculation or, rarely, hematogenous spread. Immunocompromised individuals are at higher risk.
- Inflammatory and Systemic Conditions: Rheumatoid arthritis, osteoarthritis, gout, systemic lupus erythematosus, and other inflammatory arthropathies can manifest as bursitis.
- Idiopathic Causes: In some cases, the cause of bursitis remains undetermined.
Pathophysiologically, bursitis involves the distension of the bursa with synovial fluid due to irritation. While traditionally termed “inflammatory,” not all bursitis involves primary inflammation. However, studies on subacromial bursitis reveal elevated inflammatory mediators, indicating an inflammatory component in some cases.
Clinical Presentation: Acute vs. Chronic Bursitis
Bursitis can present acutely or chronically, influencing the differential diagnosis.
- Acute Bursitis: Typically characterized by sudden onset pain, often triggered by trauma, infection, or crystalline arthropathies. Patients report localized pain exacerbated by pressure and movement. Range of motion may be limited due to pain. Skin overlying the bursa may exhibit warmth, erythema, and tenderness, particularly in septic bursitis.
- Chronic Bursitis: Often develops gradually due to repetitive microtrauma or inflammatory conditions. Swelling may be prominent, but pain might be less intense than in acute bursitis, or even painless. The bursa becomes thickened and distended over time.
Differential Diagnosis by Location
The anatomical location of bursitis significantly narrows the differential diagnosis.
Shoulder Bursitis (Subacromial Bursitis)
Shoulder pain is a frequent complaint, and subacromial bursitis is a common consideration. However, the differential diagnosis includes:
- Rotator Cuff Tendinopathy/Tears: These are extremely common and often coexist with or mimic bursitis. Pain location and aggravating factors can overlap.
- Shoulder Impingement Syndrome: Impingement of tendons and bursa in the subacromial space can present similarly.
- Adhesive Capsulitis (Frozen Shoulder): While less acute, frozen shoulder can cause diffuse shoulder pain, sometimes mistaken for bursitis.
- Glenohumeral Arthritis: Osteoarthritis of the shoulder joint can cause pain that may radiate to the bursal areas.
- Cervical Radiculopathy: Referred pain from the neck can manifest as shoulder pain.
Elbow Bursitis (Olecranon Bursitis)
Olecranon bursitis is readily apparent due to superficial swelling. Differential diagnoses include:
- Septic Bursitis: Crucially, septic bursitis must be ruled out, especially with erythema, warmth, and systemic symptoms.
- Gout/Pseudogout: Crystalline arthropathies can affect the olecranon bursa.
- Cellulitis: Infection of the skin overlying the elbow can mimic septic bursitis.
- Rheumatoid Nodules: In rheumatoid arthritis, nodules can develop near the olecranon, though these are typically firmer and less fluctuant than bursitis.
Hip Bursitis (Trochanteric Bursitis and Iliopsoas Bursitis)
Hip pain, particularly lateral hip pain, often prompts consideration of trochanteric bursitis. However, other conditions must be considered:
- Iliotibial (IT) Band Syndrome: IT band syndrome causes lateral hip and knee pain, often confused with trochanteric bursitis. Tenderness in IT band syndrome is typically more distal.
- Hip Osteoarthritis: Pain from hip arthritis can radiate to the lateral hip.
- Gluteal Tendinopathy: Tendinopathy of the gluteus medius and minimus muscles is a frequent cause of lateral hip pain and can coexist with or mimic trochanteric bursitis.
- Sacroiliac Joint Dysfunction: Pain from the SI joint can refer to the hip region.
- Iliopsoas Bursitis: Presents with anterior hip or groin pain, potentially mimicking hip joint pathology, synovitis, labral tears, or avascular necrosis of the femoral head.
Knee Bursitis (Prepatellar, Infrapatellar, Pes Anserine Bursitis)
Knee bursitis is common, with prepatellar and pes anserine bursitis being frequently encountered. Differential diagnoses include:
- Prepatellar Bursitis (“Housemaid’s Knee”):
- Septic Bursitis: Rule out infection, especially with overlying skin changes.
- Patellar Tendinitis (Jumper’s Knee): Anterior knee pain related to the patellar tendon.
- Patellofemoral Pain Syndrome: Anterior knee pain often worsened by squatting or stairs.
- Infrapatellar Bursitis (“Clergyman’s Knee”):
- Patellar Tendinitis.
- Osgood-Schlatter Disease: In adolescents, consider this apophysitis of the tibial tubercle.
- Pes Anserine Bursitis: Medial knee pain needs differentiation from:
- Medial Collateral Ligament (MCL) Sprain/Tear.
- Medial Meniscal Tear.
- Knee Osteoarthritis.
Ischial Bursitis (“Weaver’s Bottom”)
Ischial bursitis causes buttock pain, which can be mistaken for:
- Sciatica: Pain radiating down the leg along the sciatic nerve. Ischial bursitis pain is typically worse with sitting.
- Hamstring Tendinopathy: Pain at the ischial tuberosity related to the hamstring tendons.
- Sacroiliitis/Ankylosing Spondylitis: Inflammatory conditions affecting the sacroiliac joint can cause buttock pain.
Ankle and Foot Bursitis (Retrocalcaneal and Calcaneal Bursitis)
Bursitis around the ankle and heel can mimic other foot and ankle conditions:
- Retrocalcaneal Bursitis: Posterior heel pain must be differentiated from:
- Achilles Tendinopathy/Tendinitis.
- Haglund’s Deformity (Pump Bump): Bony prominence at the posterior calcaneus.
- Plantar Fasciitis: Heel pain that is typically plantar and worse in the morning.
- Subcutaneous Calcaneal Bursitis: Inferior heel pain, often related to footwear, needs differentiation from plantar fasciitis and heel spurs.
Diagnostic Evaluation for Differential Diagnosis
A thorough evaluation is essential to differentiate bursitis from other conditions.
- History and Physical Examination: Detailed history focusing on onset, location, aggravating/relieving factors, and systemic symptoms. Physical exam includes palpation for tenderness, assessment of range of motion (active and passive), and skin examination for signs of infection.
- Imaging:
- Plain Radiographs: Useful to rule out fractures, dislocations, or bone abnormalities, especially with trauma history.
- Ultrasound: Excellent for visualizing superficial bursae, fluid collections, and guiding aspiration. Color Doppler can aid in assessing for hyperemia in suspected septic bursitis.
- MRI: Superior for evaluating deep bursae and soft tissue structures, helpful when considering rotator cuff tears, labral tears, or other intra-articular pathologies.
- Bursal Aspiration and Fluid Analysis: Crucial when septic bursitis or crystalline arthropathy is suspected. Fluid analysis includes:
- Cell Count and Differential: Elevated white blood cell count (>500/mm3, particularly with neutrophil predominance) suggests infection.
- Gram Stain and Culture: To identify bacterial pathogens in septic bursitis.
- Crystal Analysis: To detect monosodium urate crystals (gout) or calcium pyrophosphate dihydrate crystals (pseudogout).
- Glucose: Low glucose levels can also be indicative of infection.
Management and Prognosis
Treatment of bursitis depends on the underlying cause and severity. Conservative management (rest, ice, compression, elevation, NSAIDs) is often effective for non-septic bursitis. Addressing underlying systemic conditions is crucial in inflammatory bursitis. Septic bursitis requires antibiotics and may necessitate drainage. Corticosteroid injections may provide symptomatic relief in non-septic cases, but risks and limitations should be considered. Physical therapy plays a role in rehabilitation and preventing recurrence.
The prognosis for bursitis is generally good, with most cases resolving with conservative management. However, recurrence is common if precipitating factors are not addressed. Septic bursitis requires prompt diagnosis and treatment to prevent complications.
Interprofessional Team Approach
Effective management of bursitis and its differential diagnosis benefits from an interprofessional team approach. Primary care physicians, sports medicine physicians, emergency medicine physicians, rheumatologists, orthopedic surgeons, nurse practitioners, and physical therapists all play vital roles in diagnosis, treatment, and rehabilitation, ensuring comprehensive patient care and optimal outcomes.
Conclusion
Bursitis is a common condition with a broad differential diagnosis. Clinicians must consider various musculoskeletal and systemic conditions when evaluating patients with suspected bursitis. A thorough history, physical examination, appropriate imaging, and bursal fluid analysis when indicated are crucial for accurate diagnosis and differentiation from mimics. Understanding the location-specific differential diagnoses and employing a collaborative interprofessional approach are essential for providing effective, patient-centered care and achieving favorable outcomes in bursitis management.
