Context: Quadriceps dysfunction is a common consequence of knee joint injury and disease, yet its causes remain elusive.Objective: To determine the effects of pain on quadriceps strength and activation and to learn if simultaneous pain and knee joint effusion affect the magnitude of quadriceps dysfunction.Design: Crossover study. Setting: University research laboratory.Patients or Other Participants: Fourteen (8 men, 6 women; age ¼ 23.6 6 4.8 years, height ¼ 170.3 6 9.16 cm, mass ¼ 72.9 6 11.84 kg) healthy volunteers.Intervention(s): All participants were tested under 4 randomized conditions: normal knee, effused knee, painful knee, and effused and painful knee.Main Outcome Measure(s): Quadriceps strength (Nm/kg) and activation (central activation ratio) were assessed after each condition was induced.Results: Quadriceps strength and activation were highest under the normal knee condition and differed from the 3 experimental knee conditions (P , .05). No differences were noted among the 3 experimental knee conditions for either variable (P . .05).Conclusions: Both pain and effusion led to quadriceps dysfunction, but the interaction of the 2 stimuli did not increase the magnitude of the strength or activation deficits. Therefore, pain and effusion can be considered equally potent in eliciting quadriceps inhibition. Given that pain and effusion accompany numerous knee conditions, the prevalence of quadriceps dysfunction is likely high.Key Words: arthrogenic muscle inhibition, central activation failure, voluntary activation, muscles
Key PointsKnee pain and effusion resulted in arthrogenic muscle inhibition and weakness of the quadriceps. The simultaneous presence of pain and effusion did not increase the magnitude of quadriceps dysfunction. To reduce arthrogenic muscle inhibition and improve muscle strength, clinicians should employ interventions that target removing both pain and effusion.
The objective of this study was to use an ovine stifle joint model to assess the impact of combined transection of the anterior cruciate and medial collateral ligaments on three-dimensional (3D) joint motion serially over 20 weeks after transection. In vivo 3D kinematics were measured in the right hind limb of eight sheep while walking on a treadmill (accuracy, 0.4 mm AE 0.4 mm, 0.48 AE 0.48). Five sheep received surgical ligament transection and three sheep received sham surgery without transection. At 2 weeks after transection, average joint flexion at hoof strike was significantly increased (8.98 AE 3.08), and the tibial position was significantly shifted in the anterior direction relative to the femur during midstance (4.9 mm AE 0.9 mm). By 20 weeks after transection, joint flexion had normalized, but the tibial position was significantly adducted (0.58 AE 0.78) and shifted in the medial (2.5 mm AE 1.2 mm), anterior (5.8 mm AE 1.9 mm), and superior directions (1.6 mm AE 0.4 mm). At 2 and 20 weeks after surgical intervention, the maximal anterior tibial position was significantly increased during mid-stance in the transected group (4.9 mm AE 0. 9 mm and 5.8 mm AE 1.9 mm) compared to the sham operated group (0.2 mm AE 0.2 mm and À0.1 AE 0.1 mm). Although the anterior tibial shift was observed in all transected sheep, a high degree of variability existed between sheep, in the intitial joint position, the magnitude of the early change, the change over time, and the change at 20 weeks. In this situation statistics must be interpreted carefully, and in future studies, individual changes should be assessed in the context of individual pathological changes in order to investigate potential clinical significance. ß
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.