Summary

Greater quadriceps rate of torque development is associated with lesser concentrations of COMP and MMP3, serum biomarkers of joint tissue breakdown

Abstract

Background

Mitigating tibiofemoral osteoarthritis development is paramount following anterior cruciate ligament (ACL) injury. Proper quadriceps function serves to absorb the energy of motion and aid in the protection of articular tissue by limiting aberrant joint tissue loading during common activities of daily living (e.g. walking) and other sport-related movements (e.g. running and jumping). Post injury muscle inhibition causes immediate quadriceps dysfunction following ACL injury and the accompanying surgery exacerbates quadriceps dysfunction making the quadriceps a critical target for post-surgery rehabilitation. Previous work has demonstrated a link between peak quadriceps torque and outcomes related to knee osteoarthritis development; however, recent studies have suggested that the ability to generate rapid muscle contractions may also be critical for attenuating energy throughout the knee at point of initial impact when the foot first strikes the ground during load-bearing activities.

Purpose

To determine the association between quadriceps strength and rate of torque development (RTD) and serum biomarkers of joint tissue breakdown (i.e. cartilage oligomeric matrix protein [COMP] and Matrix metalloproteinase-3 [MMP-3]) in patients with an ACL injury.

Methods

We included 48 patients (24 Females, 21.3±4.3years, 24.7±4.0 BMI) at a preoperative visit who sustained a primary ACL injury and were scheduled to undergo ACL reconstruction. Resting blood biomarkers and quadriceps RTD were collected at a single preoperative visit 29.1±17.1 days following ACL injury. Resting blood was collected from the antecubital fossa, processed, and stored in a -80° freezer. Upon completion of the study, stored serum samples were thawed and batch processed for COMP and MMP3 concentrations using commercially available enzyme-linked immunosorbent assays. Isometric peak strength and RTD were collected using a calibrated isokinetic dynamometer. Participants were seated on the dynamometer with their hips and knees flexed to 85° and 90° respectively and their arms folded across their chest. Following a series of warm-up trials, participants performed a maximal voluntary contraction and were cued to push into the lever arm as hard and as fast as possible. Quadriceps RTD was defined as the slope of the torque-time curve and was calculated between onset and the first 100 and 200 milliseconds (i.e., RTD100, RTD200) of the maximal voluntary contraction. Separate Pearson Product Moment correlations were used to determine the association between quadriceps peak torque, RTD100, and RTD200 with serum COMP and MMP3.

Results

Greater RTD was associated with lesser serum MMP3 (RTD100 r=-0.34, P=0.02 and RTD200 r=-0.32, P=0.03) and COMP (RTD100 r=-0.34, P=0.02 and RTD200 r=-0.32, P=0.03). There were no statistically significant associations between peak torque and serum COMP (r=0.07, P=0.66) or MMP3 (r=-0.03, P=0.82).

Discussion

Greater quadriceps RTD is associated with lesser concentrations of COMP and MMP3, serum biomarkers of joint tissue breakdown. Our results advocate for the assessment of quadriceps RTD in addition to peak torque and suggest rehabilitation practices specifically develop methods for counteracting early loss of RTD following ACL injury. Future work should determine if the addition of quadriceps power training, which is shown to improve RTD, may be more effective for maintaining joint health than strength training alone.
Funding Provider: Arthritis Foundation