Willems T.M.1, Verstraete M.2
1Ghent University, Department of Rehabilitation Sciences and Physiotherapy, Ghent, Belgium, 2Ghent University, Department of Physiotherapy and Orthopedics, Ghent, Belgium
Background: Knee osteoarthritis is a worldwide health problem and it is well known that its prevalence increases with age. Total knee arthroplasty (TKA) is frequently performed to relieve pain and disability in patients suffering from end-stage knee osteoarthritis. In literature, it has been shown that in patients with a TKA, the muscle recruitment during functional activities like sit-to-stand was altered. Cycling, however, also plays an important role in the rehabilitation of patients with a TKA. In the literature, there are some studies on the muscle recruitment pattern during cycling in healthy subjects, especially in competitive and professional cyclists, however, to our knowledge, no studies have been performed in patients. Therefore, the activation of the muscles in these patients during cycling is unknown.
Purpose: The purpose of this study was to investigate the muscle activation during cycling in patients one year after total knee replacement surgery and to compare the surgical limb to the patient's nonsurgical limb and to a matched healthy group.
Methods: Nine patients with a knee replacement (+/- one year post-operative) and nine matched control subjects performed an isokinetic knee flexion/extension strength and a cycling test during which knee kinematics and surface electromyography of the M. Rectus Femoris (RF), M. Vastus Lateralis Obliquus (VLO), M. Vastus Medialis Obliquus (VMO), M. Biceps Femoris (BF) and the M. Semitendinosus (ST) were registered. The cycling test consisted of a step-protocol at progressive resistance levels from 50 to 150 W. Differences in onset, offset, duration, timing of peak value and peak value of the five muscles were analyzed. Data were analyzed using a linear mixed model with two levels (patient/healthy group and surgical/nonsurgical limb), and the effects of group, power level and group x power level interaction were investigated while age and sex were added as covariates.
Results: Quadriceps strength was significantly lower in patients compared to the healthy control group. During cycling, significant longer muscle activity of the VMO was found in the patients surgical limb compared to their nonsurgical limb, and compared to a healthy group. Maximal peak activity of the ST was significantly higher in patients surgical limb compared to healthy controls at 150W. Next to this, there was a significant effect of power level on the maximal peak activity for all muscles being increased maximal peak activity when the power level was increased.
Conclusion(s): This investigation showed altered muscle activation during cycling in patients 1 year after TKA. Although these alteration may have been caused by muscle weakness in the knee extensors, it could impede rehabilitation and muscle recovery.
Implications: Therefore, retraining movement and activation patterns may be an important component of an effective postoperative rehabilitation program. Future work should investigate why the observed muscle activation patterns are altered, what the consequences are for other joints in the kinetic chain, whether similar patterns are present in other activities of daily living, and assess the ability of rehabilitation interventions to address neuromuscular impairments and improve overall physical performance after TKA.
Funding acknowledgements: No funding was received for this study
Topic: Musculoskeletal: lower limb
Ethics approval: This study was accepted by the Ethical Committee of the Ghent University Hospital
All authors, affiliations and abstracts have been published as submitted.
