Lower limb muscle strength in patients with low back pain: a systematic review and meta-analysis

Objective: To systematically review the published studies that compare lower limb muscle strength in patients with low back pain to matched healthy controls. Methods: We searched Medline, SciELO, Cumulative Index to Nursing and Allied Health (CINAHL), and Scopus up until December 2017. Studies comparing lower limb muscle strength in people diagnosed with low back pain to healthy control participants were included in the systematic review. Results: 14 studies, which included 951 healthy controls and 919 patients with low back pain, fulfilled the inclusion criteria. Meta-analysis revealed a lower muscle strength of hip abductor/extensors and knee extensors in patients with low back pain in comparison to healthy controls. The average strength of hip abductors (Five studies, SMD=0.7 95% CI: 0.49 to 0.9) and hip extensors (Two studies, SMD=0.93, 95% CI: 0.62 to 1.23) was significantly lower in patients with low back pain compared to that of healthy controls. Knee extensor muscle strength was significantly lower in patients with low back pain compared to healthy controls (Three studies, WMD=0.31 Nm/kg, 95% CI: 0.1 to 0.5). The meta-analysis indicated a no significant difference in knee flexor muscle strength in patients with low back pain compared to healthy controls. Conclusions: Lower limb muscle is impaired in patients with low back pain.