Abstract
Objectives:
The Anterior Cruciate Ligament Return to Sport After Injury (ACL-RSI) Scale and the International Knee Documentation Committee (IKDC) Questionnaire are reliable indicators of psychological readiness for return to sport (RTS) and knee function after anterior cruciate ligament reconstruction (ACLR), respectively. Given high re-injury rates, both psychological and physical factors should be considered during ACLR recovery. However, few studies evaluate these outcomes alongside movement quality. Previous biomechanical studies have shown that ACLR athletes shift energy absorption at the knee and hip joints when landing during a single leg hop test compared to uninjured athletes. This shift may result from altered neuromuscular control and compensatory motor patterns, indicating a lack of readiness for RTS. While muscular power and co-contraction are key in measured joint power, psychological readiness may also impact the kinematic strategy leading to compensatory motor patterns upon landing, which have not been described.
This study explored the relationships between psychological readiness, self-reported knee function and landing biomechanics following ACLR. We hypothesized that higher scores on the ACL-RSI and the IKDC would be associated with greater knee joint energy absorption due to better landing control. Patients with higher psychological readiness may be more confident in engaging the knee joint, optimizing their kinematic strategy. This relationship could serve as a marker for successful RTS outcomes, providing clinicians with a tool for personalizing individual patient rehabilitation protocols.
Methods:
Thirty-five participants (M/F: 26/9; Age: Mean ± SD = 25.26 ± 11.10 years) were included in this data analysis. Participants were measured 6-18 months postoperatively (Mean ± SD: 37.29 ± 13.46 weeks). Twenty-two had quadriceps autograft, twelve had Bone-Patellar tendon-bone, and one had hamstring autograft. ACL-RSI, IKDC, and isokinetic strength testing were administered prior to hop testing. The single leg hop for distance (SLHD) was administered bilaterally for three successful trials. Hop tests were tracked by a three-dimensional marker-based motion capture system with integrated force platforms. Thirty-five retroreflective markers were used to reconstruct an eight-segment torso and lower body model. Mechanical work of each lower extremity joint was calculated during landing from initial contact to peak knee flexion as the area under the joint power curve. Total negative joint work (NJW) represents the summed energy absorbed by the lower extremity kinetic chain and individual joint contributions were expressed as a percentage of this total.
Participants were dichotomized from ACL-RSI scores using a cutoff of 65. Normality was checked using the Shapiro-Wilk test and Independent t-tests were used to compare ACL-RSI groups for variables that met this assumption. Mann-Whitney U tests with Monte Carlo simulations compared ACLR involved limb total NJW and joint contributions to landing across groups. Cohen’s d was used to describe effect sizes for parametric tests and was interpreted as small (0.2), medium (0.5), and large (0.8) effects. Mann-Whitney effect sizes (r) were interpreted as small (0.3), medium (0.3-0.5), and large (>0.5). Alpha was set to .05.
Results:
Descriptive statistics and group comparisons are shown in Table 1. Results of the independent samples t-tests indicated no differences among high and low ACL-RSI groups for height (p=.807, d=.084), mass (p=.906, d=.041), or SLHD limb symmetry index (LSI) (p=.152, d=-.501). IKDC was significantly lower in the low ACL-RSI group (p<.001, d=-1.936). Results of the Mann-Whitney U tests indicated that the low ACL-RSI group had greater knee joint (p=.016, r=.406) and smaller hip joint contributions (p=.016, r=-.406) to total NJW on landing as compared to the high ACL-RSI group, but no significant differences in ankle joint contributions (p=.739, r=.056), total NJW (p=.714, r=.062) or time since surgery (p=.617, r=.454) were detected. Additionally, the age of participants in the low ACL-RSI was found to be significantly higher than the high ACL-RSI group (p=.007, r=.454).
Conclusions:
The results suggest that, contrary to the hypothesis, lower psychological readiness may lead to greater energy absorption of the knee joint and reduced hip involvement during landing, despite similar functional outcomes and total energy absorption in higher readiness groups. Additionally, psychological readiness did not significantly impact the symmetry between the involved and uninvolved legs. These findings underscore the importance of addressing psychological factors in rehabilitation, as they can influence movement mechanics even when overall functional symmetry is maintained.
