Clinical Measurement of Quadriceps Strength Index: Handheld Dynamometry vs 1-Repetition Maximum (ptpodcast.com)

• Quad index (side-to-side strength ratio) strongly correlates with knee function.
• HHD and 1RM tests both accurately identify ≥20% strength asymmetry.
• HHD: sensitivity 0.89, specificity 0.88; 1RM: sensitivity 0.78, specificity 0.94.
• Neither method requires expensive isokinetic equipment; 1RM can be done with leg press or extension machine.
• Study supports using these tests for clinical decision-making in knee rehabilitation.

"This article from PT Inquest discusses the clinical assessment of quadriceps strength asymmetry (quad index) using handheld dynamometry (HHD) and 1-repetition maximum (1RM) tests, based on a 2017 JOSPT study by Sinacore et al. The study found that both methods have high diagnostic accuracy for identifying meaningful asymmetries (≥20% deficit): HHD showed sensitivity 0.89 and specificity 0.88, while 1RM showed sensitivity 0.78 and specificity 0.94. The findings suggest that clinicians can reliably use either method in the clinic without needing expensive isokinetic dynamometers. The quad index remains a key predictor of knee function and return-to-sport criteria."