The five lumbar spinous processes are large and easily palpable with the spinal column in the flexed position (Fig. 10-1). The fifth lumbar vertebra is the lowest movable segment. In 5% of the population, the fifth lumbar vertebra is congenitally fused to the sacrum, a condition called sacralization. The person with this condition has only four palpable lumbar spinous processes. In other people, the first sacral segment is not fused to the other segments. This condition is called lumbarization, and six spinous processes may be palpable in the lumbar spine. A common abnormality in the lumbar spinous processes is spina bifida, a congenital defect found in 10% of the population. Spina bifida results from a failure of the vertebral arches to grow together and ossify. It is prevalent in the L5 or S1 segment. Another common abnormality in the L4 to L5 or L5 to S1 interval is spondylolisthesis. This is a fracture of the pars interarticularis that can cause forward movement of one vertebra on another.

With the patient seated and flexed forward, palpate each spinous process with your index finger and forefinger (Fig. 10-2). First look for any irregularities, such as spondylolisthesis, spina bifida, lumbarization, or sacralization. Next, place anterior pressure on each process with your thumb (Fig. 10-3) and note any rigidity or springing. Rigidity may indicate hypomobility and springing may indicate hypermobility.

The intrinsic muscles in the lumbar spine are the erector spinae group (spinalis, longissimus, and iliocostalis). In the lower spine, these muscles come together to form the sacrospinalis group (Fig. 10-4).

With the patient prone, palpate the lumbar portions of the erector spine group diagonally from medial to lateral (Fig. 10-5). Note any tenderness, inflammation, muscle spasm, or palpable bands, which may indicate muscle strain, myofascitis, fibromyalgia, or active trigger points.

The quadratus lumborum is lateral to the thoracolumbar fascia. It is attached to the transverse processes of the lumbar vertebra, the iliac crest, and the 12th rib (Fig. 10-6). It is a common site for myofascial lower back pain.

With the patient prone, palpate the quadratus lumborum from the 12th rib to the iliac crest (Fig. 10-7). This muscle is lateral to the erector spinae group. Note any tenderness, inflammation, muscle spasm, or palpable bands, which may indicate a muscle strain, myofascitis, fibromyalgia, or active trigger points.

The gluteal muscles consist of the gluteus maximus, gluteus medius, and gluteus minimus. These muscles extend, abduct, and rotate the thigh. They all originate from the ilium and insert into the femur (Fig. 10-8). They can be tender and spastic secondary to trauma. Pain can be referred to the gluteal muscles from a defect in an intervertebral disc, and they can lose muscle tone because of nerve root involvement. The gluteal muscles may have active myofascial trigger points that can refer pain to the posterior thigh, similar to a sciatic pain pattern from an L5–S1 disc defect with nerve root compression.

With the patient prone, palpate using strong pressure, starting just lateral to the sacrum and moving toward the greater trochanter of the femur (Fig. 10-9). Note any tenderness, spasm, loss of muscle tone, and tender trigger points. Tenderness and spasm secondary to trauma may indicate a muscle strain. A herniated intervertebral disc with nerve root compression may also cause tenderness and spasm to the area. An active myofascial trigger point may cause local tenderness with a referred component to the posterior thigh.

The piriformis muscle is clinically significant because of its proximity to the sciatic nerve (Fig. 10-8). It may become inflamed and spastic and compress the sciatic nerve, causing pain along the entire course of the nerve. It originates from the sacrum and inserts into the greater trochanter of the femur.

To locate the piriformis, bisect the tip of the coccyx and the posterior superior iliac spine (Fig. 10-10). This is the inferior border of the piriformis. Palpate the muscle, noting any tenderness or spasm (Fig. 10-11). If the patient has lower extremity radicular pain, note whether palpation of the piriformis increases that pain. Tenderness and spasm in the piriformis may indicate muscle strain caused by overuse. Because of the proximity of the sciatic nerve to this muscle, a radicular component to the posterior thigh may also be involved. A local tender area may indicate an active myofascial trigger point, which may also cause a radicular pain to the posterior thigh.

The sciatic nerve is composed of the nerve roots from L4 to S3. The nerve runs through the greater sciatic foramen of the pelvis through the gluteal muscles and below the piriformis (see Fig. 10-8). Once it passes the piriformis, it runs deep to the gluteus maximus midway between the greater trochanter and the ischial tuberosity. In some cases, the sciatic nerve pierces the piriformis muscle rather than passing below it.

Starting midway between the greater trochanter and the ischial tuberosity, palpate the sciatic nerve and follow the nerve as far down the lower extremity as possible (Fig. 10-12). Note any tenderness, burning, or inflammation. If the patient has any tenderness, burning, or referred pain into the extremity, suspect an irritation of the sciatic nerve.

With the patient standing and the lumbar spine in the neutral position, place one inclinometer slightly lateral to the T12 spinous process in the sagittal plane. Place the second inclinometer at the sacrum, also in the sagittal plane (Fig. 10-15). Zero out both inclinometers. Instruct the patient to extend the trunk backward. Record the inclination of both inclinometers (Fig. 10-16). Subtract the sacral inclination from the T12 inclination to obtain the lumbar extension angle.

With the patient standing and the lumbar spine in the neutral position, place one inclinometer flat at the T12 spinous process in the coronal plane. Place the second inclinometer at the superior aspect of the sacrum, also in the coronal plane (Fig. 10-17). Zero out both inclinometers. Instruct the patient to flex the trunk to one side. Record the inclination of both inclinometers (Fig. 10-18). Subtract the sacral inclination from the T12 inclination to obtain the lumbar lateral flexion angle. Perform measurements for both right and left lateral flexion.