Russell, I apologize for the delayed answer. It certainly sounds like you have piriformis syndrome, which is an compression of the sciatic nerve at the level of the piriformis muscle. This causes pain in the gluteal region that may radiate down the thighs and back of the knee. This can be due to trauma; overuse; imbalance in the surrounding muscles in the pelvis, hip, thigh and leg; problem with the sacroiliac joint; or even improper positioning of the feet. The symptoms are similar to a "pinched" nerve due to a spinal problem, but tests for spinal causes, such as a herniated disc, are normal (as seems to be the case for you). It sounds like you have tried most of the recommended modalities to try to find some relief (anti-inflammatory medications, chiropractic care, injections, physical therapy). Injections of lidocaine (a numbing agent) or botulinum toxin (botox) are sometimes used as well, as is electrotherapy. Surgery may be necessary if all these measures fail. Certainly, try to avoid any activities that tend to exacerbate the problem. An orthopedic surgeon, or perhaps even a sports medicine doctor, has expertise in this area and can do a thorough examination, review your tests and treatment, and recommend further interventions.