Effect of knee and hip position on hip extension range of motion in individuals with and without low back pain.
Level 4 - case-series / case-control
Cross-sectional case-control comparison of biomechanical measurements
PubMed 10871142 · doi:10.2519/jospt.2000.30.6.307
What was done
A 2-group mixed-design study compared 35 back-healthy subjects (24 women, 11 men; mean age 31.37 ± 11.36) and 10 subjects with low back pain (LBP) (6 women, 4 men; mean age 33.70 ± 9.31). Passive hip extension range of motion was measured across four conditions varying knee angle (full extension vs. 80° flexion) and hip angle (0° abduction vs. full abduction) to assess the contribution of one- and two-joint hip flexor muscles.
What was found
Subjects with LBP had less passive hip extension than back-healthy subjects (-5.61° ± 4.30° vs. -2.57° ± 4.18°). Across both groups, hip extension was lower with the knee flexed to 80° (-5.51° ± 4.50°) than fully extended (-0.98° ± 4.65°), and lower at 0° abduction (-7.55° ± 5.03°) than full abduction (1.06° ± 4.31°). Back-healthy subjects showed an effect of knee angle on hip extension at 0° abduction (flexed: -11.43° ± 5.81°; extended: -2.49° ± 5.39°) but not at full abduction (flexed: 1.74° ± 3.91°; extended: 1.89° ± 3.94°). Subjects with LBP demonstrated an effect of knee angle at both 0° abduction (flexed: -12.60° ± 4.91°; extended: -6.65° ± 5.03°) and full abduction (flexed: -3.10° ± 5.53°; extended: -0.10° ± 5.18°).
Why it matters
Modifying knee flexion and hip abduction during hip flexor length testing isolates the contribution of specific one- and two-joint hip flexors, which show distinct restriction patterns in people with low back pain.
Limits
The low back pain group was very small (n = 10) compared to healthy controls (n = 35). The cross-sectional design cannot establish whether altered hip flexor length causes or results from low back pain, and clinical details such as pain duration, severity, and specific diagnostic subtypes were not provided in the abstract.
Cited by
- supports Average hip hyperextension is approximately 10 degrees with bent knees and approximately 20 degrees with straight legs.