After an ankle fracture, how does cartilage die leading to arthritis?

• A. Necrosis of superficial zone cartilage at fracture sites
• B. Necrosis of deep cartilage
• C. Ischemic osteonecrosis of talus
• D. Apoptosis of subchondral bone

Answer: (A)

The question tests how cartilage death after an ankle fracture contributes to post-traumatic arthritis. When a joint surface is fractured, the cartilage at the fracture lines endures direct mechanical injury with shear and compression. The superficial zone of articular cartilage is the most vulnerable to this kind of insult, so chondrocytes there die by necrosis at the fracture sites. Because cartilage is avascular, there’s limited capacity for repair, especially in the superficial layer, so this loss creates surface irregularities, fissures, and wear that drive progressive degenerative change in the joint.

The other options don’t fit as the primary mechanism. Deep cartilage is less likely to undergo necrosis from a fracture than the superficial layer. Ischemic osteonecrosis of the talus refers to bone death from disrupted blood supply, not cartilage death contributing to arthritis. Apoptosis of subchondral bone describes bone cell death rather than the cartilage cell death that initiates the degenerative process.