Clinical Scenario Question about Osteoarthritis

Question

A 65-year-old obese woman with a diagnosis of osteoarthritis (OA) has been having increased pain in her right knee that is made worse with movement and weight-bearing and is relieved by rest. Physical examination reveals an enlarged joint with a varus deformity; coarse crepitus is felt over the joint on passive movement.  

1. Compare the pathogenesis and articular structures involved in OA with those of RA. 
2. What is the origin of the enlargement of the affected joint, the varus deformity, and the crepitus that is felt on movement of the affected knee? 
3. Explain the predilection for involvement of the knee in persons such as this woman. 

Answer 1

a. In RA, the primary pathophysiologic process ion deposition of autoantibody/antigen complexes in the joint space, leading to inflammation of the synovial membrane lining the joint space. Inflammatory mediators damage the synovial membrane and articular cartilage leading to panes (thickened synovial membrane) formation, cartilage damage and fibrosis. Inflammation may also erode bone. In OA the proces begins with loss of proteoglycans in the articular cartilage leading to fissuring, damage and eventual thinning of cartilage. Cushioning of bone ends is lost.

b.Enlargement of the joint may be due to fibrosis of the joint capsule, and the development of bone spurs. Varus deformity is due to asymmetrical loss of articular cartilage. Crepitance is due to the coarsening o articular cartilage, often of the posterior surface of thepatella, grinding against the femur or other articulating bones.

c. With weight bearing, damaged cartilage and bone is pushed together. Her obesity worsens the effects of weight bearing