Abstract
BACKGROUND: The isokinetic dynamometer is the "gold standard" equipment for assessing muscle strength after anterior cruciate ligament reconstruction (ACLR); however, its high cost limits its use in clinical practice. The hand-held dynamometer (HHD) and performance-based tests are alternative methods. HYPOTHESIS: The single leg bridge test (SLBT) and HHD are reliable and valid for assessing knee flexor strength compared with isokinetic dynamometer and knee-specific patient-reported outcomes after ACLR. STUDY DESIGN: Cross-sectional study. LEVEL OF EVIDENCE: Level 4. METHODS: A total of 127 participants with ACLR ≥6 months previously were evaluated using the International Knee Documentation Committee (IKDC) Subjective Knee Form, the Anterior Cruciate Ligament - Return to Sport after Injury (ACL-RSI) questionnaire, the SLBT, the HHD, and the isokinetic dynamometer. RESULTS: The SLBT showed good test/retest reliability in both limbs (intraclass correlation coefficient [ICC](2,1) = 0.85-0.87), moderate-to-good criterion validity with an isokinetic dynamometer (r = 0.53), and moderate-to-good construct validity with IKDC and ACL-RSI (r = 0.42 and 0.43). An HHD showed good test/retest reliability (ICC(2,1) = 0.85-0.89), moderate-to-good criterion validity with an isokinetic dynamometer (r = 0.42), and none-to-weak construct validity with IKDC and ACL-RSI (r = 0.07 and 0.23). The limb symmetry index (LSI) of the SLBT and HHD showed weak validity with the isokinetic dynamometer (r = 0.23 and 0.24). CONCLUSION: Compared with the isokinetic dynamometer, the SLBT and HHD showed good reliability and moderate-to-good validity. However, the LSIs showed weak correlations with the gold standard. CLINICAL RELEVANCE: When isokinetic testing is not possible, clinicians can use SLBT and HHD to assess knee flexor muscle strength in patients after ACLR. However, we do not recommend using the LSI of the SLBT and HHD for clinical decision making.