Many times, the hips and knees suffer the same diseases, disorders, and injuries. For example, overuse injuries such as tendinitis and chronic muscle strain are common in both the hips and knees because both joints are constantly in use. They are also both subject to acute injuries, such as sprains, strains, and dislocation.
Hip and knee pain can also be caused by referred pain from a pinched sciatic nerve, as the nerve travels through both areas. Imbalances in your stance or gait may cause abnormal stresses and premature wear-and-tear in your hips and knees, resulting in painful symptoms of arthritis.
Some painful conditions may be specific to one joint or the other. Cartilage injuries known as labral tears are specific to hip pain, while inflammation of the bursa sacs known as bursitis is a specific condition affecting the knee joint. However, painful injuries that cause instability in the hips can also affect the knees. Tight hip flexor muscles and weak gluteus medius muscles can cause the hip to rotate inward without you realizing it. This can cause painful problems such as iliotibial band friction syndrome or patellofemoral stress syndrome, as stress is put on the knee or kneecap.