When running turns into a literal pain in the butt, it's time to step back and examine where that discomfort may be rooted. Oftentimes, this type of soreness is diagnosed as piriformis syndrome. Marked by a dull ache and tightness in the gluteal muscles and oftentimes pain radiating down the back of the leg, it can range from a low-level irritation to a sidelining injury.
One of the more difficult injuries to diagnose, piriformis syndrome results from injury to or inflammation of the piriformis muscle. Located in the hip region, the piriformis is an important stabilizer muscle. "It keeps your pelvis and sacrum level and prevents your hips from internally rotating," explains Mike Orzechowski, a Fort Washington, Pennsylvania-based physical therapist and running specialist. "If you have weakness of the piriformis and glute muscles, that increased internal rotation of the hip can lead to issues and irritate the piriformis."
The difficulty in diagnosis is usually related to the similarity in symptoms between piriformis syndrome and sciatica. While sciatica is perhaps most commonly caused by a herniated disc or spinal degeneration, it can also be a result of an irritated piriformis muscle compressing the sciatic nerve. Since the nerve runs close and sometimes through the piriformis, dysfunction of the piriformis can actually cause sciatica. With that said, the pain and numbness down the back of the leg that comes with sciatica isn't always a result of piriformis syndrome. According to a recent literature review on the subject, piriformis syndrome encompasses pain and stiffness in the piriformis muscles, as well as the classic symptoms of sciatica if the muscle is irritating the nerve.
While each case is different, Orzechowski will usually have a patient he suspects has piriformis syndrome do an eccentric step down test to determine if there is weakness in that area. This simply involves standing on a step or platform on one foot and bending that knee to lower the other foot down toward the ground. If the knee of the standing leg turns inwards, it suggests there is weakness in the piriformis and surrounding muscles.
"Running is a straightforward motion, so a lot of runners forget to do cross-training and lateral exercises like lateral lunges to work those muscles," he explains. "If those hip muscles are weak and you continue to add mileage, it can become an overuse issue."