Referred Low Back Pain
Referred low back pain is hip pain that results from a problem with the low back rather than the hip itself. Pain may travel to the hip and the remainder of the leg as a result of impact to nerves as they travel through and exit the spine. Referred low back pain is more common in elderly, pregnant, and obese individuals. It may result from spinal stenosis, degenerative disc disease, or a lumbar spine fracture among other conditions.
A person suffering from referred low back pain often feels pain in the back or side of the hip and may experience numbness and tingling traveling down the leg. Findings on exam include tenderness over the low back area and pain with the straight leg raise test. X-ray and MRI, as well as nerve conduction studies are useful in the diagnosis of conditions resulting in referred low back pain. Treatment such as a steroid injection into the lumbar spine can be beneficial.
When hip pain is referred from the low back, this means that the back is the primary site of injury, but the injury results in hip pain because of the way the pain sensing nerve fibers travel within the body. The location of this “hip pain” is often in the back (buttock area) or side of the hip, in contrast to conditions of the hip joint itself, which more commonly present with groin pain. Symptoms can vary depending on the type of condition affecting the low back. Pain referred from the low back may, depending on the cause, also travel down the back of the leg and into the foot. Other symptoms may include numbness and tingling traveling from the hip down the leg to the knee or foot. Risk factors for developing referred low back pain include older age, obesity, pregnancy, and injury to the low back.
There are many conditions that cause “hip pain” referred from the low back area. One common cause is narrowing of the spinal canal (spinal stenosis) through which the nerves pass. Spinal stenosis often occurs in older individuals due to degenerative disc disease, a type of arthritis affecting the spine. A second cause of referred low back pain is when the softer cushioning disc that lies between the bony vertebrae of the spine protrudes out from the boundaries of the spine. The nerve becomes compressed as a result (herniated disc). Other conditions that occur secondary to injury are a lumbar spine fracture, stress fractures, and muscle strains. Irritation or injury from where the pelvis meets the spine (sacroiliac joint) is another cause of “hip pain” referred form the low back.
On exam, symptoms may worsen with bending movements of the spine such as bending forward or backward, rotating, and moving the spine side to side. Bending the spine backward (extension) will tend to worsen symptoms in patients with spinal stenosis. Bending the spine forward as if to touch the toes (flexion) will worsen symptoms in patients with a herniated disc. Another common exam finding is tenderness with palpation of the back due to muscle spasming around the low back. In some patients, there may be decreased or absent leg reflexes such as the knee and ankle reflex, due to the nerve being trapped or compressed at the lumbar spine. A person suffering from referred low back pain will likely experience pain with the straight leg raise test, which involves raising the extended leg toward the ceiling while lying flat on the back. This will occur in any condition where one or more of the spinal nerves is trapped or compressed.
When a condition that results in referred low back pain is suspected, it is important to review x-rays of both the hip and back. X-rays allow for the assessment of hip arthritis and for the identification of any obvious low back condition (ex. spinal stenosis). Other imaging such as an MRI may also be ordered to identify specific low back pathologies that may not show up on x-ray due to soft tissue involvement (ex. disc herniation), as well as to assess the extent of spinal stenosis if present. In addition to imaging, other testing such as a nerve conduction study can be performed to help determine the location at which a nerve is being compressed.
Non-operative treatment is the first line of defense when treating a low back condition that results in secondary hip pain. One common treatment is a steroid injection (epidural) into the lower back. Steroid injections can be both therapeutic and diagnostic in patients with suspected spinal stenosis. If an injection into the lumbar spine area provides symptomatic relief, this will confirm that the symptoms are a result of a low back condition rather than a hip condition.
Physical therapy and a home exercise program can be very helpful in treating many causes of low back pain. Strengthening and mobilizing the core muscles that surround the back and pelvis can often lead to considerable relief of symptoms. Other non-operative treatments include the use of a back brace.
Most cases of pain referred from the low back can be treated successfully without surgery. In cases where the symptoms cannot be managed with non-operative treatment, surgery may be considered. The type of surgery is dependent on the type of low back injury. Such surgeries include but are not limited to a lumbar spine fusion, microdiscectomy, laminectomy, and spinal decompression surgery. In general, surgeries of the lumbar spine are aimed at either rejoining segments of bones (ex vertebrae) to ensure proper alignment and stability –or removal and remodeling of prominent bone and tissue (ex. protruding disc). The goal of these surgeries is to relieve pressure placed on the nerves in the low back area.