Biomechanical Links Between Knee Posture, Strength, and Low Back Pain: A Narrative Review

Background: Low back pain is a major cause of disability worldwide and is increasingly understood as a multifactorial condition influenced by interactions among the lumbar spine, pelvis, hips, knees, and distal lower limbs. Although traditionally managed as a spinal disorder, biomechanical alterations in knee posture, knee range of motion, muscle strength, and neuromuscular control may affect lumbopelvic alignment, spinal loading, gait mechanics, and functional movement. Objective: This narrative review aimed to synthesize current biomechanical and clinical evidence on the relationship between knee posture, knee muscle strength, lumbopelvic alignment, and low back pain, with emphasis on kinetic-chain mechanisms and implications for assessment and rehabilitation. Methods: Relevant literature was identified through searches of PubMed, Scopus, Web of Science, Google Scholar, and ScienceDirect using terms related to low back pain, knee alignment, knee osteoarthritis, knee extension limitation, quadriceps strength, hamstring strength, lumbopelvic alignment, sagittal balance, kinetic chain, gait, lifting, neuromuscular control, and rehabilitation. Evidence from biomechanical studies, observational studies, systematic reviews, clinical trials, gait analyses, and rehabilitation literature was synthesized narratively using a kinetic-chain framework. Results: The strongest evidence supports an association between restricted knee extension, knee flexion contracture, knee osteoarthritis, sagittal imbalance, and increased lumbar loading. Biomechanical studies indicate that knee extension limitation can increase lumbar extension moments, paraspinal activation, and lumbar or thoracolumbar compressive forces during gait. Moderate evidence suggests that quadriceps and hamstring weakness may impair shock absorption and alter force transmission to the pelvis and lumbar spine. Emerging evidence supports neuromuscular and myofascial pathways linking knee dysfunction with altered trunk control, proprioception, and movement compensation. Conclusion: Knee posture, mobility, strength, and neuromuscular control are clinically relevant contributors to lumbopelvic biomechanics and low back pain. Integrated assessment and rehabilitation should address knee alignment, knee range of motion, lower-limb strength, gait mechanics, and trunk–pelvis–knee coordination