Tibial tubercle-trochlear groove (TT-TG) distance is a reliable measurement of increased rotational laxity in the knee with an anterior cruciate ligament injury.

Background: The aims of this study were: 1. To evaluate the use of the tibial tubercle-trochlear groove (TT-TG) distance as a measurement showing rotational instability after anterior cruciate ligament (ACL) injury. 2. To determine the effect of concomitant anterolateral ligament (ALL) injury on TT-TG distance.

Methods: Knee magnetic resonance (MR) images of 251 patients were retrospectively evaluated to compare the study group (131 patients) who underwent ACL reconstruction due to acute complete ACL injury and the control group (120 patients) without any trauma and/or patellofemoral instability. The rate of secondary signs of ACL injury (Anterolateral ligament injury, Kissing lesion, Anterior tibial translocation, Buckling of the posterior cruciate ligament (PCL)) in the study group was noted. The relationship between the TT-TG distance and other secondary signs was examined.

Results: TT-TG distance was measured as 10.83 ± 1.2 mm, 12.88 ± 1.1 mm, 14.17 ± 1.5 mm in control, isolated ACL and ACL + ALL groups, respectively (p < 0.05). TT-TG distance was significantly higher in the patients with ALL injury and kissing lesions than the patients without these lesions (p ˂ 0.05). TT-TG distance did not differ significantly between the patients with and without anterior tibial translocation or buckling of the PCL (p ˃ 0.05). TT-TG distance measurements showed significant interobserver 0.994 (0.992-0.996) and intraobserver 0.997 (0.996-0.998) correlation.

Conclusions: TT-TG distance measurement can be used as a reliable quantitative measure of the increased rotational instability after ACL injury. TT-TG distance increases significantly if there is an ALL injury accompanying the ACL injury.