INTRAARTICULAR TISSUE PROLIFERATION AFTER IMMOBILITY - METHODS OF ASSESSMENT AND PRELIMINARY-RESULTS IN RAT KNEE JOINTS

Objective. To develop methods to quantify intraarticular connective ti ssue proliferation after immobility and to report results in an animal model of joint contracture. Methods. Six rats had their right knee jo ints immobilized with an internal fixator for 3 weeks. The joints were harvested and sectioned. We measured the length of synovial intima an d the subintimal area with image analysis software. Proliferating syno viocytes were identified by immunohistochemistry using the ''prolifera ting cell nuclear antigen'' antibody and were counted under optical mi croscopy on whole joint sections. Two outcomes were analyzed: the subi ntimal area and a synoviocyte proliferation index (number of prolifera ting synoviocytes/synovial intima length). Both were obtained for post erior and anterior aspects of the knee. Results. Intra and interobserv er reliabilities over 87% were found with these measurement techniques . Subintimal area means were not statistically different between immob ilized and contralateral knees. In all subjects, the synoviocyte proli feration index (SPI) posteriorly was higher in immobilized than in con tralateral knees (p<0.05), due to an increase in proliferating cells ( p<0.05) rather than a change in synovial intima length (p<0.05). The S PI anteriorly was comparable in immobilized and contralateral knees (p <0.05). Conclusion. We developed methods to measure intraarticular con nective tissue proliferation in a contracture model in vivo. Prolifera tive changes in the posterior aspect of the knee suggest local mediati on of connective tissue proliferation in the contracture process. Thes e methods and preliminary results will benefit investigators assessing interventions in similar models.