What are the pathologic features of Osteoarthritis?
- Early:
- • Swelling of articular cartilage.
- • Loosening of collagen framework.
- • Chondrocytes increase proteoglycan synthesis but also release more degradative enzymes.
- • Increased cartilage water content.
- Later:
- • Degradative enzymes break down proteoglycan faster than it can be produced by chondrocytes, resulting in diminished proteoglycan content in cartilage.
- • Articular cartilage thins and softens (joint space narrowing on radiographs will be seen eventually).
- • Fissuring and cracking of cartilage. Repair is attempted but inadequate. Underlying bone is exposed, allowing synovial fluid to be forced by the pressure of weight into the bone. This shows up as subchondral cysts or geodes on radiographs.
- • Remodeling and hypertrophy of the subchondral bone results in subchondral sclerosis and osteophyte (“spur”) formation.
This pathology explains the joint space narrowing, subchondral sclerosis, cysts/geodes, and osteophytes seen on radiographs in patients with OA.
