Loaded Open Kinetic Chain Exercises Caused More Anterior Tibial Translation and Anteromedial Graft Elongation Than Closed Kinetic Chain Following Double-Bundle Anterior Cruciate Ligament Reconstruction

Context: To further improve rehabilitation programs while preventing overstretching the anterior cruciate ligament (ACL), a thorough understanding of the knee kinematics and ACL length change during closed kinetic chain and open kinetic chain (OKC) exercises is essential. The measurement of ACL graft length relates to the changes in strain experienced by the ACL graft during different types of exercises rather than simple physical length.

Objective: This study aimed to determine the effects of closed kinetic chain and OKC exercises on tibiofemoral kinematics and ACL graft length changes following double-bundle ACL reconstruction.

Design: Cohort study (diagnosis); level of evidence, 3.

Setting: Laboratory.

Patients: Fifteen patients who underwent double-bundle ACL reconstruction were asked to perform 10-kg loaded seated knee extension (OKC-10) and single-leg lunge. During the seated knee extension, patients were instructed to extend and flex the knee within a range of 0° to 90° of flexion, with a 10-kg load applied to the ankle. For the lunge, patients began in a natural standing position and were instructed to flex the ACL-reconstructed knee to approximately 90°.

Interventions: The 3-dimensional tibiofemoral kinematics under different weight-bearing conditions were determined using a dual-fluoroscopic imaging system.

Main outcome measures: The tibiofemoral kinematics in 6 degrees-of-freedom were measured. And 3-dimensional ligament simulation technique was used to quantify length changes of the anteromedial bundle and posterolateral bundle.

Results: The tibia exhibited significantly more external rotation during the OKC-10 motion than during the single-leg lunge from 35° to 70° of knee flexion (P ≤ .028). Beyond 30° of knee flexion, the tibia exhibited significantly more varus during the OKC-10 motion than during the single-leg lunge (P ≤ .028). And a significantly more anterior tibial translation was observed during the OKC-10 motion than during the lunge from 0° to 15° of flexion (P ≤ .018). The anteromedial bundle length was significantly longer during the OKC-10 motion than during the lunge between 0° and 25° of knee flexion (P ≤ .028).

Conclusions: The effects of OKC exercises with loads on knee rotational stability should be considered in making rehabilitation programs for patients after ACL reconstruction. Since some degree of anterior tibial translation is physiological, it is important to note that increased translation alone does not necessarily indicate danger or instability.