Chronic knee pain lasting three years is commonly due to conditions like osteoarthritis, which is highly manageable. For temporary relief, over-the-counter generic pain relievers like paracetamol or topical anti-inflammatory gels containing diclofenac can help ease discomfort. However, the most effective long-term treatment involves physical therapy to strengthen the muscles supporting your joint, gentle low-impact exercises, and maintaining a healthy weight to reduce joint pressure. I highly recommend consulting an orthopaedic specialist for an X-ray and a personalised treatment plan, which may include specific physical therapy or targeted prescription options. Please avoid long-term use of pain medications without medical supervision.