Alteration of knee joint connective tissues during contracture formation in spastic rats after an experimentally induced spinal cord injury.

This study was made to elucidate the changes in the periarticular connective tissue that can underlie the contracture after spasticity development. Sixteen Wistar rats underwent a spinal cord injury and 16 rats were either sham- or nonoperated. The periarticular connective tissue of the knee joint was assessed with histological, histomorphometric, immunohistochemical, and biochemical analyses. Histological results showed a smaller synovial intima, a dense subintimal and posterior joint capsule without fibrosis, and a disarranged posterior capsule in the spinal cord-injured knees with the flexion contracture. The synovial intima length was shortened only at the posterior capsule. Neither the distribution nor expression of type I and III collagen was affected. Contractures after spinal cord injuries are characterized by synovial intima adhesions. A dense and disarranged capsule may lead to joint stiffness. The alteration of periarticular connective tissues exhibits properties characteristic of the contracture after spasticity development.