2.4 Inflammatory Arthritis, Tendinopathies & Concussion

2.4 Inflammatory Arthritis, Tendinopathies & Concussion

Physical Medicine and Rehabilitation encompasses non-surgical rheumatology, sports medicine, and concussion management. Mastery of diagnostic crystal analysis, inflammatory joint patterns, tendon repair biology, and return-to-play protocols is vital for clinical board examinations.

Rheumatoid Arthritis (RA)

Rheumatoid arthritis (RA) is a chronic, systemic autoimmune disease characterized by persistent synovial inflammation (pannus formation), articular cartilage destruction, and juxta-articular bone erosions.

Joint Distribution and Deformities

RA classically presents as a symmetrical inflammatory polyarthritis affecting small joints of the upper and lower extremities:

• Target Joints: Metacarpophalangeal (MCP) joints, Proximal Interphalangeal (PIP) joints, wrist joints, and Metatarsophalangeal (MTP) joints.
• Spared Joints: Distal Interphalangeal (DIP) joints and thoracolumbar spine are characteristically spared.
• Cervical Spine Involvement: Cervical spine involved in up to 80% of patients. Transverse ligament erosion leads to atlantoaxial subluxation (C1-C2 instability). Preoperative flex-ext cervical radiographs are mandatory prior to general anesthesia intubation or cervical spine manipulation.
• Classic Hand Deformities: Swan-neck deformity (PIP hyperextension with DIP flexion), Boutonnière deformity (PIP flexion with DIP hyperextension), ulnar deviation of MCP joints, and Z-deformity of thumb.

Serology and Radiography

• Serology: Anti-Cyclic Citrullinated Peptide (anti-CCP) antibodies possess higher specificity (~95%) than Rheumatoid Factor (RF) for diagnosis and prognosticating erosive disease.
• Radiography: Periarticular osteopenia, uniform joint space narrowing, and marginal bony erosions.

Seronegative Spondyloarthropathies and Ankylosing Spondylitis

The seronegative spondyloarthropathies share common genetic, clinical, and radiographic features: negative test for RF/anti-CCP, strong association with HLA-B27, presence of enthesitis (inflammation at tendon insertion sites, such as Achilles insertion), and axial skeleton involvement.

Ankylosing Spondylitis (AS)

Chronic inflammatory arthritis predominantly affecting axial skeleton and sacroiliac joints in young adults (onset <45 years).

• Sacroiliitis: Bilateral, symmetric sacroiliitis is the radiographic hallmark.
• Spinal Fusion: Ascending marginal syndesmophytes (bony bridges connecting vertebral bodies) result in complete spinal ankylosis, known as "bamboo spine".
• Schober Test: Measures lumbar spine mobility. Marks placed at S2 spinous process and 10 cm superiorly. Flexion should increase distance by >5 cm (total >15 cm); <5 cm indicates restricted lumbar flexion.
• Extra-articular Manifestations: Acute anterior uveitis (most common extra-articular feature, ~30–40%), ascending aortitis, aortic regurgitation, and apical pulmonary fibrosis.

Crystal-Induced Arthropathies

Crystal arthropathies present with acute monoarthritis and require synovial fluid aspiration and polarized light microscopy for definitive diagnosis.

Gout vs. Calcium Pyrophosphate Deposition Disease (CPPD)

• Gout: Caused by deposition of Monosodium Urate (MSU) crystals in joints and soft tissues (tophi). Under compensated polarized light microscopy, MSU crystals appear needle-shaped and exhibit strong negative birefringence (yellow when parallel to red compensator plate axis). Classically affects 1st MTP joint (podagra).
• CPPD (Pseudogout): Caused by deposition of Calcium Pyrophosphate Dihydrate crystals. Under polarized light microscopy, CPPD crystals appear rhomboid-shaped and exhibit weak positive birefringence (blue when parallel to red compensator plate axis). Radiographic hallmark is chondrocalcinosis (linear calcification of hyaline or fibrocartilage, most commonly knee menisci, triangular fibrocartilage complex [TFCC] of wrist, pubic symphysis).

Tendinopathy Pathophysiology & Eccentric Rehabilitation

Historically termed "tendinitis," histopathological studies confirm that chronic tendon pain results from tendinopathy (tendinosis)—a degenerative process rather than active prostaglandin-driven inflammation.

Histopathology of Tendinopathy

Absence of inflammatory cells; presence of disarrayed collagen fibers, hypervascularity with neovascularization, increased mucoid ground substance, and tenocyte hyperplasia.

Eccentric Exercise Rehabilitation

Eccentric loading exercise protocols (e.g., Alfredson protocol for Achilles tendinopathy, heavy slow resistance loading) are the gold standard non-surgical intervention.

• Mechanism: Eccentric contraction applies controlled mechanical tensile stress to tendon without high peak impact forces.
• Physiologic Effect: Stimulates tenocyte mechanotransduction, promotes parallel collagen fiber alignment, increases tensile strength, reduces neovascularization, and remodels tendon matrix.

Concussion Management & Return-to-Play Protocol

Sport-related concussion (SRC) is a traumatic brain injury induced by biomechanical forces (direct blow to head, neck, or body). It reflects a functional disturbance rather than structural injury; standard neuroimaging (CT, MRI) is characteristically normal.

Diagnosis, SCAT6 Assessment and Acute Management

Diagnosis relies on clinical assessment tools such as the SCAT6 (Sport Concussion Assessment Tool 6), incorporating symptom checklists, cognitive screening (orientation, immediate memory, concentration), balance testing (Modified Balance Error Scoring System - mBESS), and neurological screening. Initial management requires brief relative physical and cognitive rest (24–48 hours) followed by gradual symptom-thresholded return to light activities.

Graduated Return-to-Sport (RTS) Step-Wise Protocol

Athletes must progress through a 6-step protocol. Each step requires a minimum of 24 hours. If any symptoms recur, athlete must stop activity, rest for 24 hours, and drop back to previous asymptomatic step.

1. Step 1: Symptom-limited activity: Daily activities that do not provoke symptoms (reading, gentle walking).
2. Step 2: Light aerobic exercise: Walking, stationary cycling at slow-to-medium pace; no resistance training.
3. Step 3: Sport-specific exercise: Running drills, skating drills; no head impact activities.
4. Step 4: Non-contact training drills: Complex training drills (passing), progressive resistance training.
5. Step 5: Full contact practice: Following medical clearance, normal training activities.
6. Step 6: Return to sport: Unrestricted normal game play.