Demographics and Posterior Knee Capsule Histologic and Genetic Characterization in Patients with Severe Knee Osteoarthritis: Comparing Those with Contracture to Those Without Contracture

Abstract

Introduction: Knee flexion contractures have a negative impact on function for patients with osteoarthritis (OA). Those with contracture treated with total knee arthroplasty (TKA) have more post-operative pain and worse outcome. Little knowledge is available about patient demographic factors or gene expression in the knee joint capsule in the setting of contracture and severe OA. // Methods: Subjects with primary severe knee OA awaiting a TKA were recruited. We collected subject demographic factors that may be associated with preoperative knee contracture. Subjects’ posterior knee capsule was harvested intraoperatively. Capsule histological analysis was performed using light microscopy. Gene expression analysis was performed using whole genome microarray and immunohistochemistry was used for protein production analysis comparing those with contracture to those without. // Results: Twenty subjects were recruited for the demographics portion of the study (13 contractures and 7 controls), and capsules from 12 subjects (6 contractures, 6 controls) were used for histology, microarray, and IHC analyses. Contracture subjects had longer duration of OA, reduced extension in the contralateral knee, and showed a trend toward elevated body mass index. Tissue cross-sectional areas of adipose, non-adipose and synovial tissues were not statistically different histologically between the two groups. There was increased expression in the contracture group for the genes CHAD, Cyr61, and Sox9. There was a corresponding increase in protein production for CHAD and Sox9. // Conclusions: Screening for OA duration and bilateral knee range of motion (ROM) could be functionally beneficial. When a knee joint contracture is present, correcting for the resulting leg length discrepancy pre- and post-operatively could improve patient outcome. Gene protein products linking capsular cells to the ECM can influence capsular fibrosis and potentially impact ROM.