Portable Dynamometry Is Reliable for Measuring Knee and Ankle Strength in Daily Practice: Results From a Systematic Review With Meta-analysis and Evidence Gap Map Using the COSMIN Methodology.

OBJECTIVE: To estimate the reliability and criterion validity of knee and ankle muscle strength measured using portable dynamometers. DESIGN: Systematic review with meta-analysis and evidence gap map. LITERATURE SEARCH: Systematic search of MEDLINE, Embase, CINAHL, SPORTDiscus, and Web of Science from inception to April 2025. STUDY SELECTION CRITERIA: We included studies that evaluated reliability or criterion validity of portable dynamometers for measuring knee extensor/flexor or ankle dorsiflexor/plantarflexor/invertor/evertor isometric strength in uninjured people or people with a lower-limb musculoskeletal condition. DATA SYNTHESIS: We performed meta-analyses for each muscle group, position, and fixation method. Methodological quality was assessed using the COSMIN (COnsensus-based Standards for the selection of health Measurement INstruments) Risk of Bias tool. Certainty of evidence was graded using a modified GRADE (Grading of Recommendations Assessment, Development and Evaluations) approach. RESULTS: We included 123 studies (n = 5042 participants); 113 studies were included in the meta-analysis. There was moderate- to high-certainty evidence of sufficient reliability (intraclass correlation coefficient ≥ 0.70) across most muscle groups, positions, and fixation methods. High-certainty evidence supported external fixation for assessing knee extensors/flexors and ankle plantarflexors. Evidence for criterion validity was sparse, and the certainty of evidence ranged from very low to high. There was high-certainty evidence of sufficient validity for knee extensor and flexor strength with external fixation in seated positions (r = 0.82-0.90). CONCLUSION: Portable dynamometers were sufficiently reliable for measuring isometric knee and ankle strength in clinical practice. The evidence for criterion validity was limited. Portable dynamometers should not yet be considered direct substitutes for isokinetic dynamometry. Reliability and validity estimates were consistent across uninjured and clinical populations. J Orthop Sports Phys Ther 2026;56(10):657-671. Epub 7 Jul 2026. doi:10.2519/jospt.2026.14091.