Common Joint Disorders

A Comprehensive Clinical Reference Guide covering Dislocation, Bursitis, Arthritis, Ligament & Meniscal Injuries, Tendon Disorders, and Clinical Red Flags.

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5.1 DISLOCATION (LUXATION)

Definition: Complete loss of contact between articulating bone surfaces of a joint. Subluxation refers to a partial dislocation where some articular contact is maintained.

Classification by Direction (Shoulder Focus):

• Anterior: Most common (>90% of shoulder dislocations); the humeral head is displaced anteriorly.
• Posterior: Less common; often associated with seizures or electrocution.
• Inferior (Luxatio Erecta): Rare; the arm is held in a fixed overhead position.

Common Sites & Key Features:

Causes:

• Trauma: Direct blow, fall on outstretched hand (FOOSH), motor vehicle accidents.
• Congenital Laxity: Developmental dysplasia of the hip (DDH), Marfan syndrome.
• Connective Tissue Disorders: Ehlers-Danlos syndrome, osteogenesis imperfecta.
• Recurrent/Pathological: Seizures (posterior shoulder), ligamentous insufficiency.

Clinical Features:

• Visible deformity with loss of normal joint contour.
• Loss of function: Inability to move the joint actively or passively.
• Severe pain at rest and with any attempted movement.
• Possible neurovascular compromise: MUST assess distal pulses, sensation, and motor function.

Management:

1. Reduction: Closed reduction (first-line) vs. open reduction (indicated for failed closed reduction, associated fractures, or neurovascular compromise).
2. Imaging: Pre-reduction X-rays (AP, lateral, axillary/scapular Y for shoulder); post-reduction films to confirm concentric reduction.
3. Immobilization: Sling-and-swath (shoulder), posterior splint (elbow), abduction brace (hip).
4. Rehabilitation: Early range of motion (ROM) to prevent stiffness; rotator cuff strengthening for the shoulder.
5. Surgical Consideration: Recurrent dislocators, young athletes, Bankart lesions — arthroscopic stabilization.

Associated Injuries to Remember:

• Bankart lesion: Anteroinferior glenoid labrum tear — increases recurrence risk.
• Hill-Sachs lesion: Compression fracture of posterolateral humeral head.
• Coronoid fracture: Part of the "Terrible triad of the elbow" (dislocation + radial head fracture + coronoid fracture).
• Sciatic nerve palsy: Occurs in 10-20% of posterior hip dislocations — check for foot drop.

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5.2 BURSITIS

Definition: Inflammation of a bursa — a small, fluid-filled sac that reduces friction between tissues (bone, muscle, tendon, skin). Bursae are strategically located at sites of potential friction throughout the body.

Common Sites & Eponyms:

Causes and Clinical Features:

• Repetitive trauma / Overuse: Occupational or sports-related.
• Infection (Septic Bursitis): Staphylococcus aureus is most common; presents with erythema, warmth, fever.
• Crystal Deposition: Gout (monosodium urate) or pseudogout (CPPD).
• Clinical Features: Localized swelling (may be fluctuant), tenderness to palpation, and pain with movement of the adjacent joint (typically worse with specific motions).

Management:

1. RICE Protocol: Rest, Ice (15-20 min, 3-4x/day), Compression, Elevation.
2. NSAIDs: Ibuprofen or naproxen to reduce inflammation.
3. Aspiration: If septic etiology is suspected — send for Gram stain, culture, cell count, and crystal analysis.
4. Corticosteroid Injection: Only after excluding infection; inject into the bursa, never the tendon.
5. Physical Therapy: Stretching and ergonomic adjustments.

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5.3 ARTHRITIS (GENERAL)

Arthritis refers to joint inflammation. While over 100 types exist, Osteoarthritis and Rheumatoid Arthritis are the most common.

5.3.1 OSTEOARTHRITIS (OA)

Definition: Degenerative joint disease characterized by progressive loss of articular cartilage, subchondral bone sclerosis, and osteophyte formation.

Pathophysiology:

• Cartilage degradation: Loss of proteoglycans leads to decreased resilience.
• Subchondral sclerosis: Bone thickening beneath cartilage.
• Osteophytes: Bony outgrowths at joint margins.

Radiographic Features (Kellgren-Lawrence Grading): Grades 0 (None) to 4 (Large osteophytes, severe JSN, definite deformity).

5.3.2 RHEUMATOID ARTHRITIS (RA)

Definition: Chronic autoimmune inflammatory arthritis characterized by symmetric synovitis, pannus formation, and progressive joint destruction.

Key Features:

• Symmetric involvement: Hands, wrists, and feet (usually spares the DIP joints).
• Morning stiffness >30 minutes: Improves with movement throughout the day.
• Rheumatoid nodules: Subcutaneous nodules over extensor surfaces.
• Treatment: DMARDs (Methotrexate first-line), biologics (TNF inhibitors), and corticosteroids for flares.

5.3.3 SEPTIC ARTHRITIS

Definition: Bacterial infection of a joint space — a MEDICAL EMERGENCY. Joint destruction can occur within 24-48 hours.

• Presentation: Acute monoarthritis (80-90% of cases), severe pain with minimal movement (patient resists any joint motion), and a hot, swollen joint.
• Management: Urgent joint aspiration for analysis. Start empiric IV antibiotics immediately after aspiration.

5.3.4 GOUT & PSEUDOGOUT (CRYSTAL DISEASES)

• Gout: Monosodium urate (MSU) crystals; needle-shaped, negatively birefringent. Classically affects the first MTP joint (podagra).
• Pseudogout (CPPD): Calcium pyrophosphate dihydrate crystals; rhomboid, weakly positively birefringent. Often affects the knee or wrist.

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5.4 LIGAMENT INJURIES

Definition: A sprain is a partial or complete tear of a ligament — the fibrous tissue connecting bone to bone.

Grading System:

1. ACL Tear (Knee):

• Mechanism: Non-contact pivoting injury, deceleration with valgus stress.
• Signs: "Pop" sound, immediate swelling (hemarthrosis within 2 hours).
• Tests: Lachman test (most sensitive: 85-95%), anterior drawer test, and pivot shift test.
• O'Donoghue's Unhappy Triad: ACL tear + MCL tear + medial meniscus tear.

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5.5 MENISCAL INJURIES

Definition: Tear of the meniscus — C-shaped fibrocartilaginous structures that provides shock absorption and stability.

Anatomy: Medial meniscus is less mobile and more commonly torn. The outer third (red-red zone) is vascularized and can heal; the inner two-thirds (white-white zone) is avascular and cannot heal.

Clinical Features:

• Joint line tenderness: The most reliable finding.
• Locking: Inability to fully extend the knee (suggests bucket-handle tear).
• Effusion: Delayed onset (hours to days), unlike ACL tears.
• Positive McMurray's test and Thessaly test.

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5.6 TENDON DISORDERS

Tendinopathy: A spectrum from inflammation (tendinitis) to degenerative failure (tendinosis) to rupture.

Common Sites:

• Supraspinatus: Rotator cuff tendinopathy (Hawkins-Kennedy test).
• Achilles: Achilles tendinopathy; overuse or fluoroquinolone use.
• De Quervain's: Tenosynovitis of the thumb (Finkelstein test).

Tendon Rupture:

Achilles Tendon: Most common major rupture; occurs during push-off. Patient reports 'being kicked in the calf.'

Thompson Test (Simmonds Test): Squeeze the calf while prone. Normal: Foot plantarflexes. Rupture: No movement.

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5.7 QUICK REFERENCE: RED FLAGS

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5.9 DIFFERENTIAL DIAGNOSIS QUICK REFERENCE

Approach to the Painful Joint:

1. Number of Joints: Monoarthritis (1 joint), Oligoarthritis (2-4 joints), or Polyarthritis (>4 joints).
2. Acute vs. Chronic: Acute is <2 weeks.
3. Inflammatory vs. Non-inflammatory:
   — Inflammatory: Morning stiffness >30-60 min, soft swelling, warmth (e.g., RA, Septic).
   — Non-inflammatory: Morning stiffness <30 min, hard/bony swelling, no warmth (e.g., OA).