Osteoarthritis

Key Features

Essentials of Diagnosis

• A degenerative disorder with minimal articular inflammation

• No systemic symptoms

• Pain relieved by rest; morning stiffness brief

• Radiographic findings

  • Narrowed joint space

  • Osteophytes

  • Increased subchondral bone density

  • Bony cysts

General Considerations

• Degeneration of cartilage and hypertrophy of bone at the articular margins

• Inflammation is usually minimal

PRIMARY

• Most commonly affects some or all of the following

  • Distal interphalangeal (DIP) joints and, less commonly, proximal interphalangeal (PIP) joints

  • Carpometacarpal joints of the thumbs

  • Hip

  • Knee

  • Metatarsophalangeal joint of the big toe

  • Cervical and lumbar spine

SECONDARY

• May occur in any joint as a sequela to articular injury

• Causes of articular injury that lead to secondary degenerative arthritis include

  • Trauma

  • Gout

  • Rheumatoid arthritis

  • Hyperparathyroidism

  • Hemochromatosis

  • Charcot joint

Demographics

• The most common form of joint disease

• 90% of all people have radiographic features of osteoarthritis in weight-bearing joints by age 40

• Patient sex is also a risk factor; osteoarthritis develops in women more frequently than in men

• Obesity is a risk factor for knee and hand (and probably hip) osteoarthritis

Clinical Findings

Symptoms and Signs

• Insidious onset

• Pain is made worse by activity or weight bearing and relieved by rest

• Bony enlargement of the interphalangeal joints is occasionally prominent

  • DIP (Heberden nodes)

  • PIP (Bouchard nodes)

• Crepitus may often be felt over the knee

• Joint effusion and other articular signs of inflammation are mild

• Because articular inflammation is minimal and systemic manifestations are absent, degenerative joint disease should seldom be confused with other arthritides

• The distribution of joint involvement in the hands also helps distinguish osteoarthritis from rheumatoid arthritis

  • Osteoarthritis primarily affects the DIP and PIP joints and spares the wrist and metacarpophalangeal joints (except at the thumb)

  • Rheumatoid arthritis involves the wrists and metacarpophalangeal joints and spares the DIP joints

• In some cases, a one-way valve effect between the knee joint and gastrocnemius-semimembranosus bursa can lead to accumulation of synovial fluid, referred to as a popliteal or Baker cyst

• No systemic manifestations

Differential Diagnosis

• Rheumatoid arthritis

• Seronegative spondyloarthropathy, eg, psoriatic arthritis

• Gout

• Chondrocalcinosis, eg, pseudogout, Wilson disease

• Other bone disease, eg, osteoporosis, metastatic cancer, plasma cell myeloma

Diagnosis

Laboratory Tests

• No laboratory evidence of inflammation such as elevated erythrocyte sedimentation rate

• Synovial fluid is noninflammatory (Table 20–2)