Well, without a clinical evaluation it would be difficult to determine the cause of the hip pain. Hip pain is often referred to the knee. Possibilities that may need to be considered include infections/ inflammations, bursitis, tendonitis, arthritis, capsulitis, ligament/ tendon tears, growths/ tumours, nerve impingement, avascular necrosis, fractures, dislocations, etc. I would suggest getting this evaluated by an orthopedician for an accurate diagnosis and appropriate management.
Hope this helps.