Instrumented Timed Up and Go Performance in Athletes with Preoperative Anterior Cruciate Ligament Rupture: A Cross-Sectional Study

Background and Objectives: Rupture of the Anterior Cruciate Ligament (ACL) in the knee may be associated with alterations in neuromuscular coordination and dynamic stability. Wearable Inertial Measurement Units (IMUs) facilitate high-resolution gait analysis, although their use in phase-specific assessment during the Timed Up and Go (TUG) test is still limited. The current study explored differences in the temporal, acceleration, and rotational parameters of an IMU-based TUG test between individuals with ACL rupture and healthy controls. Methods: In this cross-sectional observational study, 49 athletes were included: 20 individuals with ACL rupture assessed before ACL reconstruction and 29 healthy controls. A wearable IMU (G-Walk, BTS Bioengineering) was positioned at the L4 level to record the TUG task, including sit-to-stand, walking, turning, and stand-to-sit movements. Seventeen parameters were examined without a prespecified primary outcome. Results: Patients with ACL-deficient knees demonstrated longer overall TUG analysis duration than healthy controls (12.75 (1.97) s vs. 9.28 (1.06) s, p < 0.001, d = 2.32). Sit-to-stand duration was also longer (1.82 (0.22) s vs. 1.59 (0.24) s, p = 0.001, d = 0.99). Vertical acceleration during sit-to-stand was lower in the ACL group (4.89 (1.93) m/s2 vs. 6.96 (1.63) m/s2, p = 0.001, d = −1.18), whereas anteroposterior acceleration was significantly lower specifically during stand-to-sit (3.98 (0.60) m/s2 vs. 5.00 (1.77) m/s2, p = 0.007, d = −0.72). No significant difference was observed in sit-to-stand anteroposterior acceleration (p = 0.276). End-turning maximum rotation speed was also lower in the ACL group (170.35 (28.30)°/s vs. 221.30 (45.72)°/s, p = 0.001, d = −1.29). After adjustment for total TUG duration, most acceleration and rotational parameters showed no significant group differences, whereas end-turning average rotational velocity retained a nominally significant adjusted group effect in the exploratory analyses of covariance (ANCOVA), without correction for multiple comparisons. Conclusions: ACL deficiency may be associated with altered functional movement performance, although the influence of overall task performance on acceleration and turning parameters cannot be excluded. IMU-based TUG analysis may help identify functional differences relevant to rehabilitation, but its role in return-to-sport assessment remains uncertain. These exploratory findings require further confirmation.