Neuromuscular Control of Knee Laxity after an Anterior Cruciate Ligament Reconstruction

The anterior cruciate ligament (ACL) prevents anterior tibia translation relative to the femur (ATT). Annually around 0.2-4 percent of the athletes injure their ACL resulting in an increased ATT. An ACL reconstruction (ACLR) is commonly indicated as treatment. One year after ACLR, one-third of the patients do not manage to return to their pre-injured level of sports. We found that return to pre-injured sports type is higher using their own patellar tendon in the same leg compared to a donor tendon. When using a donor tendon, knee laxity (ATT) is greater. Instability due to an increase in ATT may be used in an explanation for the lower return to sports rates. In healthy subjects we found that muscle activation did not contribute in such a way that ATTd was limited at those observed knee angles, however, a smaller knee flexion angle at impact is associated with a larger ATTd. In patients after an ACLR there is a difference in landing technique between copers (patients who return to sports) and non-copers (patients who do not return to sports). Copers used larger gastrocnemius (calf muscle) activity and non-copers used smaller knee flexion moments to limit ATTd. We also found that patients with a larger medial posterior tibia plateau angle showed a lower ATTd and patients with a smaller lateral posterior tibia plateau angle showed larger maximal knee flexion angles. Patients with a larger lateral tibia plateau angle may automatically adapt their landing strategy to the anatomy of their knee