Validity and reliability of inertial measurement units on lower limb joint angles during landing and cutting tasks: A systematic review and meta-analysis.

OBJECTIVE: The use of wearable inertial measurement units (IMUs) to measure kinematic parameters of high-risk movements, such as landing and cutting, for injury prevention is becoming more common. However, the validity and reliability of IMUs in assessing lower limb joint angles still lack comprehensive validation. This systematic review and meta-analysis assessed the validity and reliability of lower limb kinematic data captured by IMUs during landing and cutting tasks. METHODS: Comprehensive searches were conducted in the Web of Science, Scopus, PubMed, and EBSCO databases up to April 10, 2025, yielding 787 studies, with an update on August 14, 2025. The included articles were assessed for quality, and a meta-analysis was performed to calculate the pooled correlation coefficients for validity and reliability. RESULTS: Eleven studies were included in the systematic review, with seven in the meta-analysis, involving 268 participants. IMUs showed good to excellent validity in measuring the knee sagittal plane angle during landing and cutting (r = 0.91-0.92, ICC = 0.80-0.90), but poor validity for the knee frontal plane angle (r = 0.39-0.41, ICC = 0.20-0.22). For reliability, the IMU-measured hip sagittal plane angle showed excellent reliability during the landing task (ICC = 0.92), while the knee sagittal plane angle, hip frontal plane angle, and knee frontal plane angle exhibited good reliability (ICC = 0.77-0.89). In the cutting task, the knee frontal plane angle showed good reliability (ICC = 0.80), but reliability for other joints was generally moderate (ICC = 0.52-0.67), and reliability was poor for the knee transverse-plane angle and hip frontal-plane angle (ICC = 0.40-0.47). CONCLUSION: IMUs showed excellent validity and reliability for knee sagittal plane angles during landing and cutting tasks. However, the validity and reliability of other measures varied, and the limited number of studies warrants cautious interpretation.