Cartilage Disorders of the Ankle

Ankle joint cartilage provides functions such as shock absorption and a low friction surface for joint movement, thereby enabling standing and walking. Ankle cartilage diseases can be categorized into two main headings: “osteochondral defects” and “ankle osteoarthritis.” Ankle osteochondral defects (OCDs) typically refer to abnormalities in the articular cartilage accompanied by subchondral bone pathology, often located on the talar side of the tibiotalar joint. It can lead to deep ankle pain upon weight-bearing, affecting daily activities and sports. Lesions might not always be detectable on standard radiographs, potentially leading to diagnostic delays if not suspected. The etiology of OCD is not fully understood, with various etiological theories existing, including traumatic, ischemic, and microtraumatic causes. Despite frequent ankle joint injuries, clinically significant ankle osteoarthritis is not as prevalent as in other weight-bearing joints. This discrepancy can be attributed to the specific anatomical, biochemical, and biomolecular characteristics of ankle cartilage. In contrast to knee or hip cartilage, ankle joint cartilage demonstrates a higher resistance to degeneration. Nevertheless, when joint congruity is compromised, leading to uneven stress and force distribution—typically observed in scenarios involving joint fractures, instability-inducing conditions, and alignment disorders—degeneration may ensue. Due to its predominantly post-traumatic etiology, patients with ankle OA tend to be younger compared to those with other degenerative joint diseases. The relationship between talus osteochondral lesions and the development of ankle OA is still debated. In this section, the unique biomechanical features of ankle cartilage, the pathophysiology of cartilage diseases, and the clinical and radiological findings of the main diseases of ankle cartilage, namely, osteochondral defects and ankle osteoarthritis, will be discussed.