Arthrogenic muscle inhibition after anterior cruciate ligament injury: Injured and uninjured limb recovery over time

Abstract

IntroductionIt is well documented that marked weakness of the quadriceps is present after knee joint injury. This joint trauma induces a presynaptic reflex inhibition of musculature surrounding the joint, termed arthrogenic muscle inhibition (AMI). The extent to which anterior cruciate ligament (ACL) injury affects thigh musculature motor unit activity, which may affect restoration of thigh muscle strength after injury, is undetermined.MethodsA randomized protocol of knee flexion and extension isometric contractions (10%–50% maximal voluntary isometric contraction) were performed for each leg on 54 subjects with electromyography array electrodes placed on the vastus medialis, vastus lateralis, semitendinosus, and biceps femoris. Longitudinal assessments for motor unit recruitment and average firing rate were acquired at 6-month intervals for 1 year post ACL injury.ResultsThe ACL-injured population demonstrated smaller quadriceps and hamstrings motor unit size (assessed via motor unit action potential peak-to-peak amplitude) and altered firing rate activity in both injured and uninjured limbs compared to healthy controls. Motor unit activity remained altered compared to healthy controls at 12 months post ACL reconstruction (ACLR).DiscussionMotor unit activity was altered after ACLR up to 12 months post-surgery. Further research is warranted to optimize rehabilitation interventions that adequately address altered motor unit activity and improve safety and success with return to sport after ACLR. In the interim, evidence based clinical reasoning with a focus on development of muscular strength and power capacity should be the impetus behind rehabilitation programming to address motor control deficits.

Neuromuscular Characteristics of Unilateral and Bilateral Maximal Voluntary Isometric Contractions following ACL Reconstruction

“…Different explanations for the disagreement in the results emerge from the comparison of the experimental design used in our study with those of others [15,20,47,50,51]. First, the ACL of the participants enrolled in the present investigation was reconstructed using the combined semitendinosus-gracilis tendon (hamstring), whereas in the studies cited above, the harvest of a bone-patellar tendon bone (BPTB) was involved.…”

“…However, in the literature, the higher hamstring activation in the ‘operated knee’ than in the ‘healthy knee’ was accompanied by quadriceps inhibition in the injured knee or on both sides during the maximal isometric contraction during the leg extension [ 15 , 20 , 47 , 50 , 51 ]. On the contrary, our study showed a higher VL (related to the peak of MVIC) and hamstring coactivation ratio (determined between VL-BF, RF-BF, and VM-BF in the initial portion of the force–time relationship, with RFD calculated with a window of 0.200 ms relative to the onset of MVICs) in the injured side than that in the uninjured side.…”

Dry Needling for Arthrogenic Muscle Inhibition of Quadriceps Femoris in Patients after Reconstruction of Anterior Cruciate Ligament: a Protocol for a Randomized Controlled Trial

“…Therefore, understanding the causes related to the deficiencies in quadriceps strength may result in early and successful management [9]. Recent Milad Zarrin, et al studies suggest that after undergoing ACLR, neural changes in electrocortical brain activity, the excitability of spinal reflex, and corticospinal pathways as well as in the central activation may contribute to the inadequate improvement of quadriceps strength and function [10][11][12]. These neural deficits have been associated with muscle weakness in the quadriceps, disordered movement patterns, and impairments in the voluntary activation of both the reconstructed and non-reconstructed limbs [10,13,14].…”