Sciatica is typically caused by nerve root compression, which can occur as a result of an intervertebral disc herniation, bone abnormalities (eg, osteoarthritic osteophytes, spondylolisthesis), spinal stenosis, or, much less frequently, an intraspinal tumour or abscess. Compression can happen in the spinal canal or the intervertebral foramen. Outside of the spinal column, nerves can be squeezed in the pelvis or buttocks. The nerve roots L5-S1, L4-L5, and L3-L4 are the most commonly affected.
Pain radiates along the length of the sciatic nerve in people with Sciatica (symptoms associated to nerve roots L4, L5, and S1), most commonly down the buttocks and posterior side of the leg to below the knee. Typically, the pain is scorching, lancinating, or stabbing. It can happen with or without lower back pain. The Valsalva manoeuvre or coughing may aggravate pain caused by a herniated disc. Patients may have numbness and, in some cases, weakness in the affected leg. Nerve root compression can result in sensory, motor, or, most objectively, reflex impairments. Ankle jerk reflex may be affected by L5-S1 disc herniation; knee jerk reflex may be affected by L3-L4 disc herniation.
