What is sciatica?
Sciatica is characterized by pain and numbness or tingling along the distribution of the sciatic nerve. It’s often confused with ordinary back or hip pain, but it’s not the same thing: sciatica is a specific pain caused by a pathology of the sciatic nerve itself. That nerve originates in the lower back (around L4–S2) and travels down the back of the hip and all the way down the back of the leg.
5 causes of sciatica
Herniated disc — the most common cause. Spinal discs cushion the vertebrae, and when one herniates or bulges, whether from an accident or stress accumulated over time, it can compress the sciatic nerve. A bulging disc or disc protrusion is the least severe version and may cause no symptoms at all; a fully herniated disc means the outer portion has torn, letting the inner material extrude and compress nearby nerves, which can send pain radiating through the back and down the legs.
Lumbar stenosis — a narrowing of the spaces within the spine, either centrally in the spinal canal or laterally where nerves exit the spine, that can compress the sciatic nerve. It presents with pain, tingling, and weakness in the lower back and legs, though it doesn’t always cause symptoms right away and is sometimes only found on an MRI or CT scan. It commonly develops from prior arthritis.
Piriformis syndrome — the piriformis is a small muscle deep in the buttock, running from the sacrum to the hip bone. Intense spasm or tightening of this muscle, often from prolonged sitting or constant pressure on the area, can irritate the sciatic nerve, which runs close by (and in some people actually runs through the muscle itself), causing sciatic pain.
Spondylolisthesis — an unstable condition where one vertebra suddenly shifts forward onto the vertebra below it, narrowing the spinal canal and compressing structures within it, including the sciatic nerve. It’s typically diagnosed with an X-ray after a history and physical exam.
What does sciatica pain feel like?
Sciatic pain has some distinguishing characteristics: it radiates from the lower back down into the legs, ranges from a mild ache to a sharp stab, is often associated with numbness in the legs or feet, rarely affects both sides of the body at once, can extend down to the foot and toes, and can be severe enough to interfere with everyday activities.
Can sciatica cause knee or hip pain?
Yes to both. The sciatic nerve travels down the back of the leg to the back of the knee, so sciatica can bring a sense of warmth around the knee, acute weakness, or difficulty fully extending the knee, usually on just one side since sciatica typically affects one side of the body. The nerve also supplies the hip and thigh area, so compression can cause hip pain directly, and off-loading weight onto the unaffected side to avoid the pain can add its own hip and thigh strain on top of it.
How is sciatica diagnosed?
Diagnosis starts with a detailed history: where the pain originates, whether it radiates, and whether there’s any numbness or tingling involved. From there, a physical examination assesses movement in the lower back, hip, and leg, nerve sensory response, muscular strength, alignment and posture, and specific nerve tests to confirm what’s driving the pain.