Hip osteoarthritis (HOA) involves progressive cartilage breakdown accompanied by synovial inflammation, though the exact histopathological consequences of synovial tissue changes in HOA are not fully understood. This study investigated the expression patterns of iNOS, BCL-2, and MMP-9 within different synovial cell types. A retrospective cohort of 32 patients was analyzed, recording demographic and anthropometric data including age, sex, height, weight, and body mass index. Synovial tissue samples were examined for the presence of lymphocytes, fibrocytes, and macrophages. Clinical and histological evaluations were performed using the OARSI cartilage grading system, WOMAC index, Kellgren–Lawrence (K-L), Harris Hip Score (HHS), Krenn score and grading. Total hip arthroplasty was carried out for all patients and control subjects, with patients stratified into groups based on OA severity. Immunohistochemical staining revealed that K-L grades and Krenn scores varied significantly across the groups, including between moderate and severe OA cases. Notably, the synovial lining thickness, resident stromal cells, and inflammatory infiltrates increased in parallel with disease severity. iNOS expression in both the intimal and subintimal layers was positively associated with Krenn scores in moderate and severe OA, while BCL-2 expression in the intima correlated with Krenn score in severe OA. These findings indicate that BCL-2, iNOS, and MMP-9 contribute to synovial pathology in HOA and underscore a link between synovial inflammation, histopathological alterations, and cartilage degeneration at the time of hip replacement for OA or femoral neck fracture.
