Background: Injury to the anterior cruciate ligament (ACL) not only causes mechanical instability but also produces proprioceptive deficit with an altered neuromuscular response. After ACL reconstruction, patients in general continue to complain of a feeling of knee instability. The objective of our study was to assess patient proprioception and its evolution over time by measuring the muscle latency time during a dynamic activity.
Methods: Twenty-five patients with an ACL tear following sports injuries were included in a prospective, comparative, matched controlled study. The study group consisted of the injured knees in those patients, while the control group consisted of the contralateral non-injured knee in the same patients. The neuromuscular response in five leg muscles (vastus medialis, vastus lateralis, rectus femoris, semitendinosus and biceps femoris) was measured during a dynamic activity through the muscle latency time via the use of electromyography.
Results: The comparison of the reaction time in the vastus medialis showed that time in the injured knee was longer at pre-op, but it reduced over time reaching a value at 6 months post-op that was close to the reaction time in the non-injured knee group. In the rectus femoris, biceps femoris and semitendinosus muscles, the reaction times in the injured knee group were similar to those in the non-injured knee group at pre-op and post-op visits.
Conclusion: Before ACL surgery, the muscle latency time of the vastus medialis was significantly longer in the injured knee group than in the non-injured knee group. 'Muscle reflex reaction' as a response during a dynamic task improved in the ACL reconstructed patients at 6 months post-op.
Level of evidence: Prospective, comparative, matched controlled study.
Keywords: Anterior cruciate ligament; Electromyography; Latency; Matched controlled study; Proprioception.