2025 Volume 16 Issue 5 Pages 763-767
Introduction: Manual muscle testing (MMT) is widely used to assess muscle strength. However, in lumbar spine disorders with L4 nerve root impairment, there are cases where patients experience giving way and difficulty in performing daily activities despite having quadriceps muscle strength rated as MMT5. This raises questions about the validity of assessing muscle weakness solely with MMT when considering surgical indications. In this study, we assessed subjective symptoms obtained through interviews, quadriceps strength assessed by MMT, and knee extension strength measured with a handheld dynamometer, to evaluate the validity of strength assessment by MMT.
Methods: Between July and September 2023, among 233 patients scheduled for surgery due to lumbar spine disorders, 82 patients were included based on the inclusion criteria. An interview was conducted, and the patients were classified into two groups: the giving-way group (Group G) and the no-giving-way group (Group C). For preoperative evaluation, knee extension strength was measured in both groups, and the affected/unaffected ratio was calculated.
Results: There were 16 cases in Group G and 66 cases in Group C. The affected/unaffected ratio of knee extension strength was 77.8% in Group G and 90.7% in Group C, indicating a higher asymmetry in Group G.
Conclusions: Approximately 20% of patients reported experiencing giving way and showed left-right differences in knee extension strength, even with a quadriceps MMT5. This suggests that quadriceps strength assessment by MMT may lack accuracy and additional patient interviews are also necessary.
