PURPOSE Single-leg landings are common in sport and often result in injury, however a rubric to evaluate biomechanics during single-leg jump landing (SLL) does not exist. The Single-Leg Landing Error Scoring System (SL-LESS) is a rubric developed to evaluate movement during SLL. The purpose of this study was to 1) determine inter- and intra-rater reliability of the SL-LESS, 2) and determine the content and construct validity of the SL-LESS when evaluating SLL

METHOD 28 healthy females completed SLL on two days while 2D and 3D data were recorded. 3D angles were trunk flexion/lateral-flexion, pelvic tilt/contralateral drop, hip flexion/adduction, and knee flexion/abduction at initial contact (IC) and maximum knee flexion (MKF). Two raters used the SL-LESS rubric to score 2D videos each day. Participants were grouped by total SL-LESS score (≤ 2 errors=good; ≥4 errors=poor landers). Kappa, prevalence- and bias-adjusted kappa (PABAK), and percent agreement were calculated for inter- and intra-rater reliability between rubric items. Total score reliability was evaluated using an ICC. Differences in 3D angles, knee abduction moment(KABDM), and vertical ground reaction force(vGRF)between good and poor landers were evaluated using a one-way ANOVA (construct validity). p

RESULTS SL-LESS item inter-rater (Average κ=0.21±0.21, PABAK=0.60±0.28, % agreement=0.78±0.13); and intra-rater (Average Κ=0.30±0.21, PABAK=0.60±0.21, %agreement= 0.79±0.12) reliability were moderate. Inter- (ICC(2,1)=0.50) and intra-rater (ICC(3,1)=0.56) reliability for total score were moderate. Good landers displayed significantly greater hip and trunk flexion at IC, and hip and knee flexion at MKF, lower KABDM at initial contact, and lower vGRF (p

CONCLUSIONS The SL-LESS can reliably be used to evaluate the SLL movement and can discriminate between “stiff” landings with upright posture and high impact force from “soft” landings with flexed landing posture with lower impact force.