Fox, Bedi, and Rodeo review the structure, composition, and biomechanical function of articular cartilage. The paper covers its four-zone architecture, ECM constituents, chondrocyte biology, viscoelastic load-bearing mechanisms, age-related changes, and MRI assessment techniques. The central question: what makes cartilage uniquely functional, and why is it so difficult to repair?
A collagen half-life of 400 years is not a trivia fact. It is the reason cartilage preservation dominates the treatment philosophy for chondral injuries, and why repair techniques remain so limited.
When you see a focal chondral defect on MRI, recognize that the sparse, non-replicating chondrocyte population cannot regenerate lost matrix. Offloading, early surgical intervention for unstable lesions, and chondroprotection are not conservative defaults — they are the biologically rational choices.
The zonal architecture has direct surgical relevance. Loss of the superficial zone eliminates tensile and shear protection for the deeper compressive zones. A full-thickness defect dismantles the mechanical hierarchy of the entire tissue column, not just the depth that is missing.
Age-related matrix dehydration increases compressive stiffness and shifts load to subchondral bone. The subchondral sclerosis and bone marrow edema you see on MRI in early osteoarthritis is a direct mechanical consequence. The bone is compensating for cartilage that can no longer deform reversibly.
Fox, Bedi, and Rodeo review the structure, composition, and biomechanical function of articular cartilage. The paper covers its four-zone architecture, ECM constituents, chondrocyte biology, viscoelastic load-bearing mechanisms, age-related changes, and MRI assessment techniques. The central question: what makes cartilage uniquely functional, and why is it so difficult to repair?
A collagen half-life of 400 years is not a trivia fact. It is the reason cartilage preservation dominates the treatment philosophy for chondral injuries, and why repair techniques remain so limited.
When you see a focal chondral defect on MRI, recognize that the sparse, non-replicating chondrocyte population cannot regenerate lost matrix. Offloading, early surgical intervention for unstable lesions, and chondroprotection are not conservative defaults — they are the biologically rational choices.
The zonal architecture has direct surgical relevance. Loss of the superficial zone eliminates tensile and shear protection for the deeper compressive zones. A full-thickness defect dismantles the mechanical hierarchy of the entire tissue column, not just the depth that is missing.
Age-related matrix dehydration increases compressive stiffness and shifts load to subchondral bone. The subchondral sclerosis and bone marrow edema you see on MRI in early osteoarthritis is a direct mechanical consequence. The bone is compensating for cartilage that can no longer deform reversibly.