What sciatica actually describes
The sciatic nerve is the largest nerve in the body. It is formed from nerve roots in the lower spine, runs through the buttock and down the back of the thigh, and divides below the knee. Irritate it anywhere along that route and the pain is felt everywhere downstream — which is why sciatica is felt in the leg when the problem is usually in the back or the buttock.
That referral pattern is also why people spend months treating a leg that has nothing wrong with it.
The causes behave differently
A herniated or bulging disc pressing on a nerve root — classically worse with sitting, bending forward, coughing or sneezing, often with a clear dermatomal pattern of numbness.
Spinal stenosis — narrowing of the canal, more common with age. Pain and heaviness in both legs that comes on with walking and eases with sitting or leaning forward.
Piriformis syndrome — the nerve compressed by a muscle deep in the buttock. Tenderness is in the buttock rather than the back, and prolonged sitting is the classic aggravator.
Sacroiliac joint dysfunction — pain referred into the buttock and back of the thigh, rarely below the knee, often worse on one side with transitions like getting out of a car.
An examination distinguishes these fairly reliably. Imaging helps confirm, but a disc bulge on an MRI in someone whose examination points to the piriformis is a coincidence, not an answer — bulges are extremely common in people with no symptoms at all.
How it is assessed here
History first: where the pain starts and where it travels, what provokes and relieves it, whether there is numbness or weakness, how it has changed. Then a physical examination — straight leg raise and its variants, reflexes, power, sensation, palpation of the spine, the sacroiliac joints and the piriformis, and how you move.
Dr. D’Alessio is board-certified in Physical Medicine & Rehabilitation, the specialty that exists to restore function without operating, and Chief Resident in PM&R at Mount Sinai Hospital. The examination is the core of the appointment rather than a formality before a scan.
Treatment
Matched to the cause. Where a muscle is the problem, a trigger point injection into the piriformis can break a spasm that stretching alone will not release. Where a joint is generating the pain, a joint injection both treats and confirms it. PRP has a role where the aim is to support healing in tissue rather than just damp down inflammation. All of it sits alongside a rehabilitation plan, because the nerve was irritated by something mechanical and the mechanics are what stop it recurring.
Pain relief that lets you move again is not the end of treatment — it is what makes the rest of the treatment possible.