A 58-year-old man with a 5-year history of right hip osteoarthritis presents with severe pain (VAS 8/10) and significant functional limitation despite 6 months of NSAIDs (naproxen 500 mg BD), physiotherapy, and weight loss of 8 kg. Radiographs show advanced OA with severe joint space narrowing and large osteophytes. He is a candidate for surgery. Before proceeding to total hip arthroplasty, what is the most appropriate next step?