Subchondral bone contribution to osteochondral health and injury.

Subchondral bone plays a critical yet often underappreciated role in osteochondral health, injury response, and the pathophysiology of osteoarthritis (OA). A limited understanding of subchondral bone behavior limits the accurate evaluation of cartilage repair outcomes. Alterations in the subchondral bone-such as changes in bone density and structure, subchondral cyst (SCC) formation, impairment of osseous microarchitecture, and overgrowth of the subchondral plate-can compromise the mechanical osteochondral unit's integrity, leading to compromised joint function and poor outcomes. Moreover, neuropathy and subchondral bone changes, both significant contributors to OA-related pain and progression, are rarely assessed in treatment strategies. A deeper understanding of subchondral bone dynamics could improve both the assessment of repair outcomes and the development of more effective therapeutic strategies for OA. In the context of cartilage procedures, clinical and translational studies revealed that up to one-third of patients undergoing microfracture or similar subchondral venting procedures exhibit clinically pathologic subchondral bone changes. These include cyst formation and upward migration of the bone plate, which negatively affect repair outcomes. Translational models further support these findings by elucidating the mechanisms of subchondral bone remodeling and its critical influence on cartilage health. This review focuses on recent translational research on the subchondral bone in both osteochondral health, injury, and OA, highlighting the need to preserve its integrity during cartilage repair and ensuring that subchondral bone is considered in OA therapy. Understanding subchondral bone alterations may guide repair strategies, including biologic therapies and biomaterial-based approaches aimed at restoring osteochondral function, paving the way for improved clinical outcomes.