Straight leg-raising testing can be both confusing and diagnostic. The SLR test ( Fig 2Z..4.-.2) can detect tension on the L5 and/or S1 nerve root. SLR may reproduce leg pain by stretching nerve roots irritated by a disk herniation. Pain below the knee at less than 70° of straight leg raising, aggravated by dorsiflexion of the ankle and relieved by ankle plantar flexion or external limb rotation, is most suggestive of tension on the L5 or S1 nerve root related to disk herniation. Reproducing back pain alone with SLR testing does not indicate significant nerve root tension.15 A CSLR sign occurs when contralateral leg elevation produces sciatic pain in the symptomatic leg. Crossover pain is a stronger indication of nerve root compression than pain elicited from raising the straight painful limb. A markedly positive SLR in the younger patient is more likely associated with a prolapsed intervertebral disk than in an older patient, particularly when it is associated with a positive CSLR.
FIG. 274-2. Instructions for the straight leg-raising (SLR) test. 1. Ask the patient to lie as straight as possible on a table in the supine position. 2. With one hand placed above the knee of the leg being examined, exert enough firm pressure to keep the knee fully extended. Ask the patient to relax. 3. With the other hand cupped under the heel, slowly raise the straight limb. Tell the patient, "If this bothers you, let me know, and I will stop." 4. Monitor for any movement of the pelvis before complaints are elicited. True sciatic tension should elicit complaints before the hamstrings are stretched enough to move the pelvis. 5. Estimate the degree of leg elevation that elicits complaint from the patient. Then determine the most distal area of discomfort: back, hip, thigh, knee, or below the knee. 6. While holding the leg at the limit of straight leg raising, dorsiflex the ankle. Note whether this aggravates the pain. Internal rotation of the limb can also increase the tension on the sciatic nerve roots.
Additional confirmatory maneuvers include an exacerbation of pain with foot dorsiflexion or with the addition of head flexion with the SLR maneuver held at the symptomatic limit of sciatic pain tolerance. In the older patient, positive SLR or CSLR tests are less specific as to pain etiology but do suggest a radicular component of involvement.19 Sitting knee extension (Fig.,2.74:3) can also test sciatic tension. The patient with significant nerve root irritation tends to complain or lean backward to reduce tension on the nerve.15
FIG. 274-3. Instructions for sitting knee extension test. With the patient sitting on a table, both hip and knees flexed at 90 degrees, slowly extend the knee as if evaluating the patella or bottom of the foot. This maneuver stretches nerve roots as much as a moderate degree of supine SLR.
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