The effectiveness of an exercise programme on knee loading, muscle co-contraction, and pain in patients with medial knee osteoarthritis: A pilot study ☆ , ☆☆ Lara Al-Khlaifat a,b, ⁎, Lee C. Herrington a , Alison Hammond a , Sarah F. Tyson c , Richard K. Jones a a School of Health Sciences, University of Salford, Salford M66PU, UK b Faculty of Rehabilitation Sciences, University of Jordan, 11942 Amman, Jordan c School of Nursing, Midwifery and Social Work, University of Manchester, M13 9PL, UK abstract article info Article history: Received 10 September 2014 Received in revised form 29 March 2015 Accepted 31 March 2015 Available online xxxx Keywords: Exercise Osteoarthritis Loading Co-contraction Background: Knee loading, muscle co-contraction, and pain are increased in knee osteoarthritis (OA). Exercises decreased pain in knee OA, yet OA is a mechanical disease and biomechanical changes need to be explored as well. Therefore, this study aims to investigate the effectiveness of an exercise programme on these outcomes in people with medial knee osteoarthritis. Methods: Cohort pilot study design. Nineteen participants with knee OA attended group exercise sessions, integrated with self-management education, once a week for six weeks, with additional home exercises. Outcomes assessed pre- and post-exercise programme were: External Knee Adduction Moment (EKAM), Knee Adduction Angular Impulse (KAAI), knee antagonist muscle co-contraction during gait, and the pain-subscale of the Knee injury and Osteoarthritis Outcome Score (KOOS). Results: Fourteen participants completed the study. Post-exercise intervention, the EKAM and KAAI did not change significantly (p = 0.21–0.7, p = 0.56, respectively). Muscle co-contraction between the vastus-lateralis and biceps-femoris muscles decreased in early-stance (64.78 (44.35) compared to 38.10 (23.10), p = 0.01) and mid-stance (27.62 (32.12) compared to 14.94 (17.40), p = 0.04). A corresponding significant pain reduction was seen (p = 0.00) with a median and range of 51.50 (47.00–62.50) at week six compared to 34.50 (29.25– 41.25) at baseline. Conclusion: This is the first known study to explore the effect of an exercise programme on knee loading and mus- cle co-contraction in knee OA. Although EKAM did not change, the findings suggest a reduction in vastus-lateralis and biceps-femoris co-contraction might be a mechanism by which pain is reduced in knee OA. © 2015 Elsevier B.V. All rights reserved. 1. Introduction Medial knee osteoarthritis (OA) is more common than lateral knee OA [1] because of the pattern of loading on the knee joint [2]. This is determined by the magnitude of the external knee adduction moment (EKAM) [3] which is the turning force generated when the tibia rotates medially with respect to the femur in the frontal plane and is a measure of the extent of varus deformity. Knee loading is also represented by the knee adduction angular impulse (KAAI) during gait, which takes into account the temporal variable throughout the stance phase (area under the curve) and not the peaks at certain points only [4]. The EKAM is related to pain, disease progression and severity of OA [5,6]. However, recent reports suggest merely reducing the EKAM does not reduce the medial compressive forces through the knee and that co- ordination of the musculature around the knee (the co-contraction) should also be considered as knee antagonist muscle co-contraction is increased in knee OA compared to healthy individuals [7,8]. The increased co-contraction corresponds to a more generalised muscle activity, whereas lower co-contraction indicated more selective activation [9]. However, this increase might be a protective mechanism to improve knee joint stability during gait in the presence of muscle weakness with knee OA [10]. Knee stability is needed during mid- stance when the ‘screw home mechanism’ activates the Biceps Femoris to externally rotate the tibia and achieve full knee extension [11]. Also, this increase in co-contraction between the knee flexors and ex- tensors when combined with the reduced range of flexion/extension The Knee xxx (2015) xxx–xxx ☆ Disclosure of funding: this study was funded by The University of Jordan and The University of Salford. ☆☆ ISCRTN number: 61720526. ⁎ Corresponding author at: Room 304, Faculty of Rehabilitation Science, Physiotherapy department, University of Jordan, 11942 Amman, Jordan. Tel.: +962 796161493 (Work). E-mail addresses: L.Khlaifat@ju.edu.jo, L.Al-Khlaifat@edu.salford.ac.uk (L. Al-Khlaifat). THEKNE-02069; No of Pages 7 http://dx.doi.org/10.1016/j.knee.2015.03.014 0968-0160/© 2015 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect The Knee Please cite this article as: Al-Khlaifat L, et al, The effectiveness of an exercise programme on knee loading, muscle co-contraction, and pain in patients with medial knee osteoarth..., Knee (2015), http://dx.doi.org/10.1016/j.knee.2015.03.014