Spinal stenosis and disc herniation are common problems causing impingement of the lumbar nerves. This can happen to any of the nerves in the lumbar spine, although the sciatic nerve is most commonly affected. Pressure on the sciatic nerve causes pain that radiates from the lower back through the buttocks and the back of the leg, according to the Mayo Clinic. Sciatica can also cause numbness or weakness in the leg. It often affects only one side of the body.
Spinal stenosis is the narrowing of the spinal canal. According to the American Academy of Orthopaedic Surgeons, arthritis often causes this narrowing to occur. As the spinal canal narrows, the nerves of the spinal cord in the lumbar region become irritated and cause symptoms of sciatica.
Lumbar disc herniation can also cause similar symptoms. The Johns Hopkins School of Medicine explains that intervertebral discs made of cartilage separate the individual vertebrae of the spine. Age or injury can cause a disc to rupture or herniate. Cartilage from a ruptured disc can press on the lumbar nerve roots, causing pain, weakness and numbness. Symptoms caused by spinal stenosis and disc herniation may be treated conservatively with treatments such as physical therapy. However, some cases do require surgical intervention.