Long distance runners don't retire - they just slowly grind to a halt. One of the most common causes of this painfully slow grind to a halt is buttock pain and sciatic pain that radiates down the back of the leg.
The cause of this pain may be the piriformis muscle which is located deep in the buttock. When this muscle locks up, so does the whole hip and the underlying sciatic nerve can be impinged, thus causing pain that radiates down the leg. An inflamed piriformis is often associated with a previous or current back injury. An experienced therapist is able to palpate this muscle and determine if it is in spam.
Once a muscle is in spasm, it will tend to stay that way. In fact, it will begin to adapt to that condition so that spasm becomes its norm. The environment of a muscle in spasm is toxic due to the very poor blood flow through it. Over time, the muscle becomes hard, gristle-like, crunchy, swollen and very tender to press. It is weak and prone to cramping.
The usual treatment is trigger point therapy in the form of acupuncture, acupressure and maybe deep tissue massage. Stretching the gluteals and piriformis are mainstays for prevention and treatment.
In my experience, the most effective remedy is deep tissue massage of the affected muscle and all of the associated muscle groups. It works; but it must be given time: An hour per session and repeated at least 6-8 times every 4-5 days until pain free. This must be supported by nutritional strategies to ensure that there is maximum healing between sessions. In most cases, there must be measures to reduce body acidity because the body may be overwhelmed by the sudden influx of metabolic toxins that are being squeegied out of swollen muscles. It is not unusual for a person, such affected, to feel ill for a few days following this kind of massage.
Once full function and health is restored to the affected muscles it is a good preventive measure to have weekly massages to keep the body in good health. This is of increasing importance as we get older.