Analysis of Neuromuscular Control and Sensory and Psychological Anxiety Affecting Shock Absorption Capacity in Patients After Anterior Cruciate Ligament Reconstruction Surgery.

Background: Patients who have undergone anterior cruciate ligament (ACL) reconstruction surgery are at high risk of re-injury and osteoarthritis due to increased impact during landing. The characteristics of patients after reconstruction surgery include significant co-contraction of the knee joint antagonistic muscles, decreased proprioception of the knee joint, and psychological anxiety. However, it is unclear whether these factors are related to shock absorption capacity during landing. The purpose of this study was to investigate whether neuromuscular control and sensory and psychological anxiety are associated with shock absorption capacity during single-leg landing from a 30 cm platform in patients who had undergone ACL reconstruction. It was hypothesized that patients with significant knee co-contraction, knee proprioceptive impairment, and psychological anxiety would have reduced shock absorption capacity during landing. Study Design: Descriptive Laboratory Study. Methods: This study included 16 patients who had undergone ACL reconstruction surgery after sustaining a sports-related ACL injury involving landing movements. Patients with concomitant meniscal or cartilage injuries were excluded. The subjects performed single-leg landings on a force plate from a height of 30 cm, and the shock absorption capacity and magnitude of co-contraction of the quadriceps and hamstrings were measured, and a co-contraction index (CCI) was calculated. In addition, the degree of knee joint proprioception impairment was measured using a Joint-Position Sense test (JPS test), and the level of psychological anxiety related to return to sport was assessed using the Anterior Cruciate Ligament-Return to Sport after Injury (ACL-RSI) scale. Multiple regression analysis was used to examine whether there was a relationship between outcomes and the shock absorption capacity during landing. Results: The participants consisted of 16 patients (6 males and 10 females) with a mean age of 21.1 ± 2.4 years. Both the CCI and proprioceptive ability (JPS test) significantly influenced the loading rate during landing (R² = 0.70, p < 0.01), with a greater effect observed for CCI (β > JPS). No association was observed with the degree of psychological anxiety in the patients. Conclusions: This study demonstrated that greater co-contraction of the knee joint antagonist muscles and reduced proprioceptive ability were associated with decreased shock absorption capacity during single-leg landing in patients after ACL reconstruction. # Level of Evidence 3.