Reliability and Validity of a Wall Sit Test for Monitoring Growth-Related Lower Limb Pain in Elite Youth Footballers

To develop and evaluate the reliability and validity of a novel Wall Slide Test for monitoring pain and knee flexion in youth athletes with growth-related lower-limb pathologies. Reliability and prospective longitudinal cohort study. A Category 1 English Premier League football academy. Eighty-one male academy footballers aged 9–17 years with clinically diagnosed lower-limb pain conditions (including Osgood–Schlatter disease, patellofemoral joint pain, Sinding-Larsen–Johansson syndrome, and Sever’s disease) and 45 asymptomatic controls. Pain at onset of loaded knee flexion (0–10 numerical rating scale), knee flexion range (cm), and a composite Wall Slide Test score. Reliability was assessed using intraclass correlation coefficients (ICC), standard error of measurement (SEM), and minimum detectable change (MDC). Validity was evaluated using mixed-effects models and receiver operating characteristic (ROC) analysis. Within-day reliability was excellent (ICC = 0.96–0.97). MDC values indicated meaningful detectable change (pain 0.74 points; range 9.1 cm). The composite score demonstrated good to excellent discriminative ability between symptomatic and asymptomatic players (AUC = 0.81–0.94). The Wall Slide Test is a simple, reliable, and valid field-based tool for monitoring pain and functional knee flexion in youth athletes, supporting clinical decision-making and longitudinal management. • Developed an objective Wall Slide Test for adolescent footballers. • Test shows excellent reliability across repeated within-day sessions. • Detects meaningful week-to-week symptom and function changes. • Discriminates symptomatic athletes from pain-free controls. • Simple, field-ready tool to guide injury monitoring in youth sport.