My Clinical Notes

• Characterised by progressive erosion of articular cartilage
• Considered to be an intrinsic disease of articular cartilage in which biochemical and metabolic alterations result in its breakdown
• Primary osteoarthritis
  • No initiating cause
  • Oligoarticular
• Secondary osteoarthritis
  • 5%
  • Generally involves prior trauma to a joint or developmental deformity or underlying systemic disease such as diabetes, ochronosis, haemochromatosis or marked obesity
  • Generally involves one joint
• Knees are more affected in women, hips are more affected in men

Pathogenesis

• Aging and mechanical effects – evidence from the fact it occurs with increasing age, occurs in weight bearing joints, there is an increased frequency in joints which due to disease conditions are exposed to abnormal mechanical stresses such as obesity and previous joint deformities
• Genetic factors – particularly involving arthritis of the hips and hands. Linkage to chromosome 2 and 11.

• Disease is characterised by significant changes in both the composition and mechanical properties of cartilage
• Early in disease, the degenerating cartilage contains increased water and a decreased concentration of proteoglycans compared with healthy cartilage. There is also a weakening of the collagen network due to decreased synthesis of type II collagen and increased breakdown of pre-existing cartilage
• There is also an increase in apoptosis probably resulting in a decrease in chondrocytes

• Altogether these changes result in a decrease in tensile strength and resilience of articular cartilage

Morphology

• Initially the superficial layers of cartilage are degraded due to the biochemical changes which result in an increased water content and reduced concentration of proteoglycans
• At this stage the articular surface is granular and softer than normal
• Eventually full thickness portions of cartilage are sloughed off and friction smoothes the articular bone giving it the appearance of polished ivory (bone eburnation)
• Concurrently there is rebuttressing and bone sclerosis
• Dislodged cartilage and subchondral bone form loose bodies in the joint
• Synovial fluid is forced into subchondral regions to form fibrous walled cysts
• Osteophytes develop at the margins of the articular surface and are capped with fibrocartilage and hyaline cartilage that gradually ossifies

Clinical course

• Characteristic symptoms are deep achy pain which worsens with use
  • Morning stiffness
  • Crepitus
  • Limitation of range of movement
• Osteophytes can impinge on spinal foramina resulting in cervical and lumbar nerve root compression with radicular pain, muscle spasms, muscle atrophy ad neurological deficits
• Joints commonly affected are;
  • Hips
  • Knees
  • Lower lumbar and cervical vertebrae
  • Proximal and distal interphalangeal joints
  • First carpometacarpal joints
  • First tarsometatarsal joints in the feet

This entry was posted on Sunday, November 18th, 2007 at 4:45 pm and is filed under Orthopaedics. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.