Beyond Distance: A Simple Qualitative Assessment of the Single-Leg Hop Test in Return-to-Play Testing

Background: Limb symmetry index in the single-leg hop (SLH) test has been questioned for its low predictive value in identifying secondary anterior cruciate ligament (ACL) injury. The purpose of this study was to describe a qualitative 2-dimensional (2D) scoring system for the assessment of the SLH test and associate it with the vertical ground-reaction forces (vGRF) and sagittal plane biomechanics evaluated through gold standard 3D motion analysis. Hypothesis: Stiff landings would be associated with low 2D scores. Study Design: Descriptive laboratory study. Level of Evidence: Level 4. Methods: Thirty-four competitive football (soccer) players (age 22.8 +/- 4.1 years, 16 women) were enrolled. Each athlete performed a series of SLH tests. Three-dimensional motion analysis was recorded using 10 stereophotogrammetric cameras, a force platform, and 3 high-speed cameras. The 2D qualitative assessment was performed through a scoring system based on the video-analysis of sagittal plane joint kinematics. A score of 0/2 (inadequate), 1/2 (partially adequate), or 2/2 (adequate) was attributed to the movement, based on objective measurements. The vGRF was extracted from the force platform and grouped according to the results of the 2D evaluation. Results: Significantly higher vGRF (stiffer landing) was found for athletes obtaining a 0/2 score compared with those obtaining a 2/2 score (up to 0.8 body weight higher, P < 0.01). A significant negative rank correlation was found between the vGRF and the total score (rho = -0.17, P = 0.03). Conclusion: The qualitative scoring system effectively identified stiff landings in the SLH for distance test.