Lumbar Decompression is Associated With Changes in Functional Transition Biomechanics and Neuromuscular Control During Sit-to-Stand in Degenerative Lumbar Stenosis

Study Design Prospective cohort study. Objectives To compare sit-to-stand (STS) movement patterns and characterize neuromuscular activation and compensatory strategies in patients with degenerative lumbar stenosis (DLS) before and after lumbar decompression, relative to healthy controls. Methods Thirty-five DLS patients undergoing central decompression and sixteen healthy controls were included in the study. Patients were evaluated one week preoperatively and three months postoperatively; controls were tested once. STS kinematics and muscle activation were quantified using three-dimensional motion capture and surface EMG across three trials without upper-extremity assistance. Outcomes were analyzed using linear mixed-effects regression models adjusted for age and body mass index, with subject-level random intercepts. Results At peak trunk forward lean, postoperative patients shifted toward a lower-extremity–driven strategy, with greater knee flexion, reduced pelvic anterior tilt, and reduced thoracic flexion (25.9° vs 30.4°, p < 0.001). Neuromuscular coordination improved postoperatively. Normalized EMG findings reflect relative activation patterns and should not be interpreted as absolute muscle effort. Tibialis anterior activation occurred earlier (4.6% vs 10.1%, p = 0.002) with lower mean activity, suggesting improved anticipatory ankle control. Gluteus maximus showed earlier onset (2.9% vs 9.0%, p = 0.018), longer activation duration ( p = 0.001), and lower mean amplitude (0.9 vs 1.8, p = 0.002), reflecting more efficient hip extension. Erector spinae activation was delayed (9.3% vs 4.3%, p = 0.031) with reduced duration ( p = 0.003), indicating decreased reliance on protective trunk co-contraction. Patient-reported outcomes improved significantly, including disability (ODI: 24.8 vs 44.4), fear of movement (TSK: 36.2 vs 43.4), physical function (PROMIS PF: 42.3 vs 35.1), and pain interference (PROMIS PI: 57.3 vs 66.2) (all p < 0.001). Conclusion Lumbar decompression was associated with measurable changes in functional transition biomechanics and neuromuscular coordination during sit-to-stand. Postoperatively, patients demonstrated reduced reliance on trunk-dominant compensatory strategies and protective extensor co-contraction, with greater lower-extremity contribution and improved anticipatory neuromuscular control. Importantly, these objective recovery signatures were detected despite minimal differences in task completion time, suggesting that conventional time-based assessments may underestimate meaningful postoperative functional recovery. Objective biomechanical assessment of activities of daily living may provide a sensitive measure of recovery following lumbar decompression and may help guide postoperative rehabilitation and functional optimization in patients with degenerative lumbar stenosis.