If you have ever experienced a muscle spasm down the back of your leg, or pain or numbness radiating from your hamstring, you may suffer from piriformis syndrome. Although the piriformis is a very small muscle lying deep in the musculature of your hip, it can put an end to your running regimen, and even make it painful even to walk. If you think you may be suffering from this condition, here is a brief explanation of the symptoms and their cause.

The piriformis is a small short piece of muscle tissue buried deep within the muscles of the hip, and runs from the pelvis to the top of the femur. The primary purpose of the muscle is to rotate the leg externally when the hip is extended, and rotates the leg internally when the hip is flexed. The most important purpose of this muscle is to rotate the knee outward when running and walking to give your body more stability.

However, the problem with this muscle lies in the fact that it lies immediately next to the sciatic nerve. This is a thick bundle of nerve tissue running from the base of the spinal under the gluteus muscle and down the back of the leg, delivering all of the nerve signals along the backside of the legs all the way to the feet. This nerve is what allows all of the muscles in the backs of your legs to fire at the right time and with the right intensity.

When the piriformis muscle becomes irritated and inflamed, it rubs against the sciatic nerve causing it to become irritated and inflamed as well. In a small percentage of the human population, the sciatic nerve and piriformis muscle are actually intertwined, with the nerve running through the muscle. In these individuals cases of piriformis infection syndrome are much more common.

According to the classical definition of the syndrome, the primary symptom is a feeling of soreness, tightness, or aching in the buttocks, rear of the pelvis, or at the top of the femur. However, many patients also experience numbness, tingling, or weakness that radiates from the lower back down through the hamstrings and calves. These symptoms may be exacerbated by periods of prolonged sitting.

Runners may experience pain in their buttocks, especially through the stage phase of the running stride. The pain will likely intensify when running faster, and when going up or down hill. Since piriformis syndrome is so closely related to identical symptoms found in sciatica, the two can be hard to tell apart and diagnose properly. Luckily there are a few tests you can perform to determine if you have infection in the piriformis or the sciatic nerve.

The straight-leg raise test is one such test. To perform it, simply lie on your back, and have a partner raise your straight leg up to as close to 90 degrees as your comfortable with. If you feel a shooting pain down the back of your leg during this stretch, it is often indicative of sciatic nerve inflammation. To test for piriformis infection, lie down on your back with your arms at your side. Have your partner rotate your foot and leg inward. Pain in this area indicates inflammation of the piriformis.