An 84-year-old man presented with hip pain following a fall. He had a background of osteoarthritis, hypertension, and diabetes mellitus. Plain X-ray imaging excluded a fracture, and he was admitted for analgesia and physiotherapy. He was given regular paracetamol, tramadol 50mg QDS, and PRN oramorph. 3 days later, the physiotherapist reported that his rehabilitation was being limited by ongoing pain on weight-bearing. What is the most appropriate next step in his management?