Functional Deficits in Non-elite Soccer (Football) Players: A Strength, Balance, and Movement Quality Assessment After Anterior Cruciate Ligament Reconstruction.

Introduction: Anterior cruciate ligament (ACL) reconstruction (ACLR) is the gold standard for treating ACL injuries, particularly in soccer players who are at a high risk of knee injury. While professional athletes often return to sport (RTS) within 7-10 months after ACLR, non-elite players experience significant delays. There is a need to investigate neuromuscular deficits and functional asymmetries in the non-elite group, which may persist even after clearance for RTS. This study aims to evaluate the functional movement patterns, single-leg balance, and isokinetic knee strength in non-elite soccer players preparing to RTS. Additionally, correlations between the aforementioned parameters were explored.

Methods: A cohort of 69 male, non-elite soccer players (mean age: 24.32±8.56 years) who underwent ACLR with a hamstring graft was recruited. Functional assessments were conducted at the mean time of nine months post-surgery, and all participants were clinically cleared by the surgeon. The evaluation included the Functional Movement Screen™ (FMS), single-leg balance tests (SLBT) on stable and unstable platforms, and isokinetic strength tests (IST) for knee flexion and extension at 60 deg·s and 180 deg·s. Limb symmetry indices (LSIs) were calculated. Statistical analyses included t-tests, Mann-Whitney U tests, and Spearman correlations.

Results: The mean FMS score was 15.45±2.23, indicating moderate functional movement quality. SLBT results revealed no significant (P>0.05) inter-extremity differences in stability indices, regardless of platform setting (stable or unstable). However, significant deficits in quadriceps and hamstring strength were observed in the ACLR extremity. At 60 deg·s, the mean peak torque/body weight (PT/BW) ratio for knee extension was 2.01±0.65 Nm.kg for the ACLR side versus 2.60±0.57 Nm.kg for the contralateral side (P<0.0001). Similar asymmetries were observed at 180 deg·s (1.51±0.44 vs. 1.88±0.35 Nm.kg; P<0.0001). LSIs for quadriceps were markedly reduced, averaging 76.97±17.72% at 60 deg·s and 79.89±17.11% at 180 deg·s. At 60 deg·s, the mean PT/BW ratio for knee flexion was 1.24±0.34 Nm.kg for the ACLR side versus 1.39±0.32 Nm.kg for the contralateral side (P=0.009) at 180 deg·s (1.03±0.27 vs. 1.16±0.25 Nm.kg; P=0.003). LSIs for the hamstring were averaging 89.34±13.91% at 60 deg·s and 88.44±14.58% at 180 deg·s. Weak negative correlations were found between FMS scores and stability indices (e.g., r=-0.26 for overall stability index on unstable platform; P=0.031), while moderate positive correlations were observed between PT/BW ratios and FMS scores (r=0.36-0.60; P<0.001).

Conclusions: Significant strength asymmetries in quadriceps and hamstring muscles persist in non-elite soccer players after ACLR. While balance deficits were minimal, weak correlations between FMS scores and stability indices suggest a link between functional movement quality and dynamic control. These findings highlight the need for targeted strength training in rehabilitation and the importance of comprehensive assessments, including functional performance tests, strength evaluations, and balance analysis, to ensure safe RTS. Achieving clinical clearance does not equate to full recovery, emphasizing the necessity for a multidimensional approach to RTS decisions.