Hyaluronic acid and chondroitin sulfate content of osteoarthritic human knee cartilage: Site‐specific correlation with weight‐bearing force based on femorotibial angle measurement

This study analyzed glycosaminoglycan (GAG) content in specific compartments of the knee joint to determine the impact of malalignment and helped refine indications for osteotomy. To assess malalignment, the radiological femorotibial angle (FTA) was measured and knee joints were also graded for OA severity with the Kellgren/Lawrence (K/L) classification. Cartilage samples were obtained from 36 knees of 32 OA patients undergoing total knee replacement surgery. Explants were harvested from the medial femoral condyle (MFC), lateral femoral condyle (LFC), patellar groove (PG), and lateral posterior femoral condyle (LPC). Concentrations of hyaluronic acid (HA) and chondroitin sulfate (CS) were measured by high‐performance liquid chromatography (HPLC). With OA severity, the average FTA significantly increased. HA and CS content in MFC was negatively correlated with radiographic FTA. In LFC, HA ratio, which is HA content in lateral condyle divided by medial condyle and chondroitin 6 sulfate, increased until about 190° FTA. Importantly, at >190° these contents were significantly decreased. HA and CS content of the femoral condyle shows topographic differences that are related to OA grade and weight‐bearing force based on FTA. The clinical relevance is that osteotomy may not be indicated for patients with severe varus (>190°) abnormalities.