The Pathophysiology and Progression of Hip Osteoarthritis Accompanied with Joint Pain are Potentially Due to Bone Alterations - Follow-up Study of Hip OA Patients

OBJECTIVES This study examined hip osteoarthritis (OA) patients with joint pain and accompanying signal changes detected by magnetic resonance imaging (MRI). METHODS A total of 19 hip OA patients with suddenly occurring or worsening pain regardless of Kellgren-Lawrence grading were enrolled. The patients were monitored using MRI, plain radiographs, and the Denis pain scale for a minimum of 6 months. The patients were classified into 2 groups: those whose pain improved during conservative treatment (Group A) and those whose pain persisted (Group B). RESULTS Joint pain disappeared or was markedly improved in all 10 cases in Group A. Radiographic OA progression occurred in 7 of 8 cases with available radiographs. Hip MRI was performed on 7 of 10 patients, among whom bone signal changes disappeared in 6 patients. One patient exhibited persisting bone signal alterations although joint pain had completely disappeared. In Group B, joint pain remained in all 9 cases. Radiographic OA progression occurred in 8 of 9 cases, and local (4 cases) or broad (5 cases) bone signal alterations were present in end-point MRI examinations. Two patients exhibited different regional MRI bone signal changes (local or broad) at the end of follow-up. The mean age of Group B was significantly higher than that of Group A. CONCLUSION THIS STUDY UNCOVERED THE FOLLOWING OBSERVATIONS: 1) hip OA with joint pain had bone alterations that were detectable by MRI, 2) these bone alterations disappeared when joint pain improved, 3) bone alterations remained when joint pain continued, and 4) radiographic OA progressed to a more advanced stage over a short time period. These findings indicate that the pathophysiology of OA, joint pain, and OA progression may primarily be due to bone changes.