Sciatica is a symptom, not a diagnosis, referring to pain, tingling, or numbness caused by the irritation or compression of a spinal nerve root, typically in the lower back (L4-S3) due to a herniated disc. This compression is known as lumbar radiculopathy and creates a specific neurological pattern following the path of the sciatic nerve. However, many conditions, both spinal and non-spinal, can produce pain that closely mimics this classic pattern. Understanding these alternative causes is important because effective treatment depends entirely on accurately identifying the source of the irritation.
Piriformis Syndrome
Piriformis Syndrome causes sciatic nerve symptoms originating in the deep gluteal region, not the spine. The piriformis is a small muscle deep in the buttock connecting the sacrum to the femur. The sciatic nerve typically passes beneath this muscle, but sometimes passes through it. When the piriformis becomes tight, inflamed, or spasms, it can directly compress or irritate the sciatic nerve. Symptoms include pain, tingling, and numbness radiating from the buttock down the back of the leg, mimicking true sciatica.
Distinguishing Features
A primary feature is the aggravation of pain by activities that tense or compress the muscle. Pain increases with prolonged sitting, especially on hard surfaces, which puts direct pressure on the nerve. Movements involving external rotation of the hip or direct palpation over the muscle often reproduce the leg pain. Irritation can result from acute trauma, such as a fall, or chronic overuse from activities like running or cycling. Diagnostic maneuvers, such as the FAIR test (Flexion, Adduction, and Internal Rotation of the hip), are used to provoke pain by stretching the piriformis, helping differentiate it from a disc issue.
Sacroiliac Joint Dysfunction
Pain mimicking sciatica can originate from the sacroiliac (SI) joint, which connects the sacrum to the pelvis (ilium). SI joint dysfunction, or sacroiliitis, involves inflammation or abnormal movement of this joint, causing lower back and buttock pain that can radiate down the back of the thigh. This pain is typically centralized around the posterior hip and buttock, often described as a sharp or stabbing sensation.
Differentiation from Sciatica
A significant difference is that SI joint pain rarely extends below the knee, unlike true radiculopathy which often reaches the foot or toes. This referred leg pain stems from irritation of surrounding ligaments and the joint capsule, not direct sciatic nerve compression. Symptoms are aggravated by movements that stress the pelvis, such as standing up, twisting, or rolling over in bed. Activities involving single-leg stance, like climbing stairs, also intensify discomfort. Crucially, SI joint dysfunction lacks the true neurological signs of nerve root compression; patients usually do not exhibit muscle weakness or changes in reflexes. Diagnosis is supported by physical provocation tests that reproduce the pain by stressing the joint.
Lumbar Spinal Stenosis
Lumbar spinal stenosis is a spinal condition causing leg pain via neurogenic claudication. It involves the narrowing of the spinal canal or the nerve root openings (foramina), usually due to age-related degenerative changes like thickened ligaments and bone spurs. This narrowing space restricts the nerves traveling down the spinal canal.
Neurogenic Claudication
The leg symptoms—including pain, heaviness, cramping, or numbness—are entirely activity-dependent. Discomfort is consistently brought on by walking or prolonged standing and is often bilateral, affecting both legs simultaneously. This pain forces the individual to stop walking after a predictable distance, a pattern known as claudication.
The most reliable differentiating sign is positional relief. Symptoms are consistently relieved by sitting down or flexing the spine forward, such as leaning over a shopping cart. This forward flexion temporarily increases the spinal canal diameter, reducing pressure on the nerves. Conversely, standing upright or extending the spine backward narrows the canal and quickly aggravates the pain. This pattern contrasts with acute sciatica or Piriformis Syndrome, where pain is often constant or worsened by sitting. Stenosis is progressive, meaning the walking distance before symptoms begin tends to decrease over time.
Vascular Causes of Leg Pain
Leg pain involving cramping or aching during walking can be caused by peripheral artery disease (PAD), a circulatory problem. PAD leads to vascular claudication, which is often mistaken for neurogenic pain like sciatica or spinal stenosis. PAD occurs when atherosclerosis narrows the arteries supplying blood to the legs.
Vascular Claudication
The pain results from muscle ischemia—a temporary lack of oxygen supply to the leg muscles during exertion. When muscles demand more oxygenated blood during walking, narrowed arteries cannot deliver it quickly enough. This mismatch causes a deep ache or cramp, usually in the calf muscles, forcing the person to stop and rest.
The defining difference from neurogenic pain is the method of relief. Vascular pain is relieved only by complete rest, allowing muscle oxygen demand to decrease. The position of the spine or leg, such as sitting or bending forward, has no effect on relief. Vascular causes are often accompanied by objective signs of poor circulation, including a decrease or absence of peripheral pulses in the foot, skin discoloration, and poor healing of sores. Recognizing these circulatory signs is important because PAD is a systemic vascular disease and carries serious health risks.