A 52-year-old woman with a 10-year history of osteoarthritis of the right knee presents with progressive pain, morning stiffness lasting 30 minutes, and functional limitation affecting her activities of daily living. She has failed conservative management including NSAIDs, physiotherapy, and intra-articular corticosteroid injections over the past 6 months. On examination, she has varus deformity, crepitus, and restricted range of motion. Plain radiographs show Kellgren–Lawrence Grade 3 osteoarthritis. What is the most appropriate next step in management?