Open AccessCo‐contraction in RA patients with a mobile bearing total knee prosthesis during a step‐up task
Author(s) -
Garling Eric H.,
Wolterbeek Nienke,
Velzeboer Sanne,
Nelissen Rob G. H. H.,
Valstar Edward R.,
Doorenbosch Caroline A. M.,
Harlaar Jaap
Publication year - 2008
Publication title -
knee surgery, sports traumatology, arthroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.806
H-Index - 125
eISSN - 1433-7347
pISSN - 0942-2056
DOI - 10.1007/s00167-008-0537-7
Subject(s) - prosthesis , medicine , thigh , kinematics , rheumatoid arthritis , knee joint , contraction (grammar) , orthodontics , physical medicine and rehabilitation , surgery , physics , classical mechanics
It was hypothesized that rheumatoid arthritis (RA) patients with a total knee prosthesis that allows axial rotation of the bearing (MB) will show more co‐contraction to stabilize the knee joint during a step‐up task than RA patients with a fixed bearing total knee prosthesis (FB) where this rotational freedom is absent while having the same articular geometry. Surface EMG, kinematics and kinetics about the knee were recorded during a step‐up task of a MB group ( n = 5), a FB group ( n = 4) and a control group ( n = 8). Surface EMG levels of thigh muscles were calibrated to either knee flexion or extension moments by means of isokinetic contractions on a dynamometer. During the step‐up task co‐contraction indices were determined from an EMG‐force model. Controls showed a higher active ROM during the step‐up task than the patient group, 96° versus 88° ( P = 0.007). In the control group higher average muscle extension, flexion and net moments during single limb support phase were observed than in the patient group. During the 20–60% interval of the single limb support, MB patients showed a significant higher level of flexor activity, resulting in a lower net joint moment, however co‐contraction levels were not different. Compared to the control group arthroplasty patients showed a 40% higher level of co‐contraction during this interval ( P = 0.009). Control subjects used higher extension moments, resulting in a higher net joint moment. Visual analysis revealed a timing difference between the MB and FB group. The FB group seems to co‐contract approximately 20% later compared to the MB group. RA patients after total knee arthroplasty show a lower net knee joint moment and a higher co‐contraction than controls indicating avoidance of net joint load and an active stabilization of the knee joint. MB and FB patients showed no difference in co‐contraction levels, although timing in FB is closer to controls than MB subjects. Since visual analysis revealed a timing difference between the MB and FB group, this may express compensation by coordination. Rehabilitation programs for RA patients should include besides muscle strength training, elements of muscle‐coordination training.