Some Biochemical and Biophysical Aspects of Joint Stiffness

Abstract

Flexion contrac-tures of canine and rat knee joints produced by extra-articular internal fixation are the result of changes in collagen tissue on the volar aspect of the joints. Connective tissue from the volar surface of joints with flexion contractures contains approximately twice as much hydroxy-proline as similar tissue from mobile joints. There is no significant difference in the thermal shrinkage temperatures of collagen from contracted as compared to normal joints. An increase in natural and artificial cross-linking of articular collagen can produce a change in joint mobility. The magnitude of change in mobility produced by insertion of additional cross-links is not great enough to account for clinically significant joint stiffness. Gross, microscipic and biochemical evidence for new collagen synthesis was demonstrated as the fundamental process in the pathogenesis of joint stiffness. Surgical removal of newly synthesized collagen from areas around stiff human interpha-langeal joints produces immediate relief of flexion contractures. Long-term results of removal of excess collagen from stiff joints were not satisfactory because of subsequent collagen synthesis during healing.