The articularis genu as a surrogate for structural determinants of peri-articular myopenia in osteoarthritis.

The functional limitations associated with the painful stiffness of knee osteoarthritis (kOA) can affect the muscles of the knee, such as the quadriceps femoris (QF) and articularis genu (AG). The vastus medialis oblique (VMO) of the QF complex is particularly sensitive to kOA. The AG, which can be sampled during total knee arthroplasty (TKA) for kOA, can provide information about the condition of the QF when affected by patient-reported disuse, helping to identify indicators of muscle weakness in the synovial fluid. This study compares the structural and gene expression changes between the VMO and the AG collected from patients with advanced kOA at the time of TKA. The histological measurements were validated using quantitative polymerase chain reaction to analyze the expression of genes related to myofiber characteristics and fibrosis. The results showed similar distribution and size changes in muscle fibers and collagen deposition in the AG compared to the VMO. This suggests that the AG can be used to study kOA-related changes in the medial QF. These findings could help develop personalized rehabilitation strategies for kOA patients by examining the relationship between AG characteristics and the local secretion of myokines and growth factors related to muscle health, allowing for practical synovial fluid analytics to assess the health of articular muscles before TKA.