Differences in timing and magnitude of lumbopelvic rotation during active and passive knee extension in sitting position in people with and without low back pain: A cross-sectional study.

Repetitive lumbopelvic rotation (LPR) during active limb movements has been indicated as a factor that contributes to low back pain (LBP). Prior studies suggest that people with LBP demonstrate greater and earlier LPR during limb movements in prone. We examined timing and magnitude of LPR during sitting active knee extension in people with and without LBP. We also investigated differences of LPR during active and passive knee extension in LBP group. 38 men (mean age: 38.4)10.6) years) with chronic mechanical LBP and 38 matched healthy men (mean age: 36.6(8.4) years) were examined. Kinematic data were collected by motion capture system and analyzed using OpenSim software. The difference between the start time of knee extension and start time of LPR was calculated and was normalized to knee extension movement time. Maximum angular displacement for LPR was also calculated across time. People with LBP demonstrated earlier LPR during knee extension than healthy subjects (P < 0.01). There was, however, no difference in maximum LPR between groups. LBP group also demonstrated greater and earlier LPR during active than during passive knee extension (P < 0.01). Earlier LPR during limb movements in sitting may be related to LBP. Quadriceps muscle activity and inefficient trunk muscles activation may contribute to early LPR in LBP group. A greater understanding of the factors that may contribute to early LPR during daily activities can provide information to guide rehabilitation treatment for people with LBP.