Ultrastructural changes in dog femoral condylar cartilage following anterior cruciate ligament section.

Canine femoral condylar cartilage from stifle joints subjected to surgical division of the anterior cruciate ligament showed conspicuous, widespread alterations in chondrocyte morphology and matrix organisation when compared by transmission electron microscopy with cartilage from sham-operated and non-operated joints. Chondrocyte changes were of a kind associated with increased synthesis of matrix components; zone I cells lost their flattened shape and became rounded, cells in zones I and II developed an extensive endoplasmic reticulum, occurred in pairs more often than usual and were situated in enlarged electron-lucent lacunae. Associated with altered chondrocyte function and increased hydration, the matrix became increasingly disorganised; collagen fibrils were widely separated, disorientated and of small diameter. It is postulated that the disorder is primarily one of inappropriate cell function.