Comparison of four tests of quadriceps strength in L3 or L4 radiculopathies.

STUDY DESIGN This prospective cohort study evaluated four office tests of quadriceps strength in symptomatic adults with radiographic evidence of L3 or L4 nerve root compression. OBJECTIVE The study observed the performance of each test for its ability to detect quadriceps weakness when compared to the asymptomatic side. To determine the potential influence of radicular pain on the performance of the four tests, a control group of patients over the age of 40 with clinical and radiographic L5 or S1 radiculopathies underwent identical testing of quadriceps strength. SUMMARY OF BACKGROUND DATA The L3 and L4 nerve roots innervate the quadriceps; therefore, quadriceps weakness may be a consequence of L3 or L4 radiculopathies. There are no standardized or validated methods to evaluate quadriceps strength in the clinical office setting. This may lead to inconsistent detection by clinicians of quadriceps weakness in cases of L3 or L4 radiculopathy. METHODS Thirty-three consecutive patients with L3 or L4 radiculopathies and 19 with L5 or S1 radiculopathies were studied. The four tests of quadriceps strength included: 1) single leg sit-to-stand test; 2) step-up test; 3) knee-flexed manual muscle testing; and 4) knee-extended manual muscle testing. Results from a second examiner repeating the four tests were used to calculate interrater reliability. RESULTS In L3 and L4 radiculopathies, unilateral quadriceps weakness was detected by the single leg sit-to-stand test in 61%, by knee-flexed manual muscle testing in 42%, by step-up test in 27% and by knee-extended manual muscle testing in 9% of patients. The sit-to-stand test detected weakness in all but one case when weakness was detected by another test. All patients with L5 or S1 radiculopathies could perform the sit-to-stand test. Kappa coefficient was high for sit-to-stand test (0.85), step-up (0.83), and knee-flexed manual muscle testing (0.66), and low for knee-extended manual muscle testing (0.08). CONCLUSION In L3 and L4 radiculopathies, unilateral quadriceps weakness was best detected by a single leg sit-to-stand test. Patients of similar age with radicular pain caused by L5 or S1 radiculopathies could perform this test. As the interrater reliability of the single leg sit-to-stand test is high, clinicians should consider utilizing this test for assessing quadriceps strength in cases of L3 and L4 radiculopathies.