Define Osteoarthritis. Describe its clinical features, investigations, management and complications.

Definition

Osteoarthritis (OA) is the commonest joint disease — a degenerative disorder of synovial joints characterised by progressive loss of articular cartilage with accompanying subchondral bone changes, osteophyte formation and secondary synovitis. It is best regarded as a whole-joint failure rather than simple ‘wear and tear’. It may be primary (idiopathic) or secondary to a pre-existing abnormality (trauma, dysplasia, avascular necrosis, previous infection or inflammatory arthritis).

Pathology

The initiating event is cartilage damage: fibrillation and softening progress to fissuring and full-thickness loss, exposing bone. The subchondral bone responds with sclerosis (eburnation) and cyst formation, while at the joint margins new bone and cartilage form osteophytes. A secondary low-grade synovitis and capsular fibrosis contribute to pain and stiffness.

The four cardinal radiographic features of OA — remembered as ‘loss’: Loss of joint space, Osteophytes, Subchondral sclerosis and Subchondral cysts.

Clinical Features

Typically an older patient with activity-related joint pain that is relieved by rest, short-lived (<30 min) morning stiffness or ‘gelling’ after inactivity, and progressive loss of function. Examination shows crepitus, bony enlargement, restricted movement and, later, deformity (e.g. Varus knee) and instability. The commonly affected joints are the knee, hip, first CMC joint of the thumb, and the dip joints (Heberden’s nodes) and PIP joints (Bouchard’s nodes) of the hand.

Investigations

The diagnosis is largely clinical and radiographic. Plain radiographs show the ‘loss’ features: Loss of joint space (usually asymmetrical), Osteophytes, Subchondral sclerosis and Subchondral cysts. Blood tests are normal (helping to exclude inflammatory arthritis); joint aspiration is done only to exclude infection or crystals.

Management

Treatment is a stepwise, largely conservative programme. Non-pharmacological: patient education, weight loss, exercise and physiotherapy (quadriceps strengthening for the knee), activity modification, walking aids and footwear/orthoses. Pharmacological: topical NSAIDs and paracetamol, oral NSAIDs (with gastric caution), and intra-articular corticosteroid injections for flares. Surgical options for advanced disease refractory to conservative care include osteotomy (to realign and offload a compartment in the younger patient), arthroplasty (joint replacement — the definitive treatment for end-stage hip and knee OA) and arthrodesis (for selected small joints).

Complications

Progressive pain, deformity (varus knee, fixed flexion), instability, muscle wasting and loss of function and independence. Complications of treatment include the risks of NSAIDs and of joint-replacement surgery.

• Degenerative whole-joint disease: cartilage loss + subchondral changes + osteophytes.
• Mechanical pain (worse with use), brief (<30 min) morning stiffness, bony swelling, crepitus.
• Hands: Heberden’s (dip) & Bouchard’s (PIP) nodes; also knee, hip, thumb base.
• X-ray ‘loss’: Loss of space, Osteophytes, Sclerosis, Subchondral cysts.
• Conservative first (weight loss, exercise, analgesia); arthroplasty for end-stage disease.