Psychosocial factors after anterior cruciate ligament reconstruction (ACLR) are garnering increased attention for their role in knee function and return to sport. Lack of confidence has been related to decreased knee function, yet the effects of confidence on strength and hop performance in younger adults following ACLR are not well defined.
PURPOSE: To compare quadriceps strength and hop test performance between individuals who are confident and those who lack confidence in their knee 3 years after ACLR.
METHODS: 45 individuals 3 years post ACLR (22 males, 23.2±5.0 years, BMI 25.0±3.8) participated. Based on their Likert scale response to the question “How much are you troubled with lack of confidence in your knee?” from the Knee Injury and Osteoarthritis Outcome Score (KOOS), participants were divided into “Confident” and “Not Confident” groups [Confident answered “not at all” (n=27) vs. not confident answered “mildly” or “moderately” (n=18)]. Quadriceps strength was quantified as the peak of 3 maximal volitional isometric contractions at 60° knee flexion for the involved and uninvolved limbs. A clinical hop testing battery was performed: 3 tests for distance [single hop (SH), triple hop (TrH), triple crossover hop (CH)] and 1 test for time [timed 6 meter hop (TiH)]. Three trials were performed and averaged for each limb. The hop and strength data were log transformed to satisfy normality assumptions and compared with analyses of variance and covariance.
RESULTS: Quadriceps strength was not different between groups. Confident individuals performed better on all hop tests except the involved SH [Mean difference (cm or sec), p-value; Involved: SH 17.3, p=.09; TrH 69.3, p=.05; CH 74.8, p=.017; TiH 0.24, p=.025; Uninvolved: SH 22.8, p=.017; TrH 77.8, p=.017; CH 73.8, p=.031; TiH 0.30, p=.008]. After controlling for height, weight and quadriceps strength, differences between groups persisted for the involved CH (p=.036) and TiH (p=.05), and uninvolved SH (p=.03), and TiH (p=.05).
CONCLUSIONS: Those who lacked confidence had worse hop performance 3 years after ACLR. Although quadriceps strength was not different between groups, controlling for strength affected the differences in hop performance between groups. The interplay between strength, hop performance and confidence requires further investigation.
Supported by NIH 5RO1AR053684 (KPS) and OSU Sports Medicine, Sports Health and Performance Institute (SHPI) Grant (LCS).