Identification and Targeting of Collagen in the Capsule of Rat Knees with Immobilization-Induced Flexion Contractures

Abstract

Immobility causes joint contractures, loss in range of motion (ROM), notably in elderly and bed-ridden patients. In a rat knee immobilization flexion contracture (FC) model, the posterior capsule contributes to irreversible limitation of ROM. Through microarray, extracellular matrix and collagen pathways were identified as differentially expressed in the posterior capsule of knees with FC. We hypothesized that intra-articular injection of collagenases in rats with knee FC will interfere with collagen in the capsule and allow increased ROM. After four weeks of hind-limb immobilization, rats develop knee FC; two weeks of remobilization with collagenase treatment showed increased ROM compared to buffer injected knees of 8.043° (p-value=0.046). Histological analysis of knee sections revealed changes in collagen content of the extracellular matrix in posterior capsule. In vitro incubation of rat capsules with collagenases confirmed changes in collagen. Along with current rehabilitation methods, treatment with collagenase may augment ROM recovery from knee joint contractures.