Knee joint overloading is identified as a major risk factor for the development or progression of knee osteoarthritis (OA). If you or your patients are having a hard time managing their mass and staying light on their feet, this can have consequences for the load on the lower extremity joints during weight-bearing activities. Studies support that there is likely an optimal “window” of loading where too much is detrimental and too little is also detrimental. So, you just don’t want to stop loading your joints because this can be equally problematic for joint function. Luckily for many, there are initiatives around the world that are trying to understand the role of gait modifications to alter the knee joint loading environment during walking. We want to keep people away from needing surgery, either realignment surgery through high tibial osteotomy or a total knee replacement. From previous posts on this blog, we know that knee replacements cannot be the answer to our knee OA problem. It is therefore important to develop conservative treatments that prevent, or at least delay the necessity for surgery.
Over the past two decades, there have been ebbs and flows of work on using gait modifications that aim to reduce detrimental knee joint loading. The most prevalent location of knee OA is on the medial (or inner) side of the knee joint. Therefore, a number of studies have focused on reducing the loading on this medial side of the joint. Several gait modifications have been identified to reduce this loading; altering step width, trunk lean, foot progression angle and medializing the knees.
These gait modifications have been tested using state-of-the-art measurement equipment to calculate knee joint loading through biomechanics and muscle activation. Of all the measures that we take, the net external knee adduction moment (KAM) – an identified proxy for medial knee joint loading is the most widely used. This is a promising approach, because the magnitude of the KAM has been related to the presence, severity and progression of medial knee osteoarthritis. For those interested in the calculation, it is often thought of as the product of the ground reaction force in the frontal plane and its moment arm to the knee joint center in the frontal plane. For everyone else; Greater KAM is associated with greater medial compartment loads.
Research has shown that it is possible to teach people with medial knee osteoarthritis a gait pattern that reduces the KAM and this leads to positive results such as pain reduction and improved functioning (Hunt and Takacs 2014; Shull et al. 2013). However, treatment outcomes were only investigated for short-term effects and concern has been expressed relating the effect of changes in other variables and their effect on long-term joint function. Participants did report muscle soreness for the first 1 to 3 weeks of the training programs mentioned previously. Muscle soreness may arise from an increase in muscle activation as a result of the training program. It is intuitively understood that muscle forces will change as a result of altering the gait pattern. Muscles that span the knee will increase loading on the knee joint when they contract and if they are worked too much, may also cause fatigue.
At the VU Medical Center in Amsterdam, The Netherlands we are investigating this gait retraining intervention. Our first results have focused on muscle activation patterns as a result of the modified gait and have been published:
Booij MJ, Richards R, Harlaar J, Rutherford D, van den Noort J. Knee muscle activation patterns are altered in patients with moderate knee osteoarthritis during gait retraining designed to reduce the knee adduction moment. Podium presenter at the 25th European Society for Movement Analysis in Adults and Children; 2016 September 29; Seville, Spain.
Main points: Patients with medial knee osteoarthritis were able to apply a gait pattern that reduced their KAM by at least ten percent after a single training session. However, this modified gait led to an increase in activation of knee spanning muscles. These elevated activations have implications for increased knee joint loading and musculature fatigue, both of which would not be favorable to long-term application.
At the VU University Medical Center we are currently working on a follow-up study, investigating a longer training program. Gait retraining is performed on a GRAIL system (Gait Real-time Analysis Interactive Lab, Motek ForceLink). Patients receive real-time feedback on the magnitude of their knee adduction moment as they walk with the goal of reducing KAM.
The aim is to see whether patients are capable of maintaining the modified gait pattern after a six week training program, with follow-up measurements at three and six months. If these patients are well acquired to their modified gait after six months, do their muscle activation patterns revert back to a normal level? This may have implications for the long-term adaptation to gait modification strategies.
This blog was written by Ms. Marjolein Booij (MSc. Human Movement Sciences). She recently graduated from the Research Master Human Movement Sciences. As part of Marjolein’s training, she was a visiting research student in the Joint Action Research Lab, School of Physiotherapy at Dalhousie University, sponsored in part by Jo Kolk and Anna Fonds Scholarships. Currently she is still part-time involved in the follow-up study at the VU University Medical Center, which is funded by KNEEMO (European initial training network for knee osteoarthritis research).
Hunt MAA, Takacs J. Effects of a 10-week toe-out gait modification intervention in people with medial knee osteoarthritis: A pilot, feasibility study. Osteoarthr. Cartil. 2014;22(7):904–11. Available from: http://dx.doi.org/10.1016/j.joca.2014.04.007
Shull PB, Silder A, Shultz R, Dragoo JL, Besier TF, Delp SL, et al. Six-week gait retraining program reduces knee adduction moment, reduces pain, and improves function for individuals with medial compartment knee osteoarthritis. J. Orthop. Res. 2013 Jul;31(7):1020–5. Available from: http://onlinelibrary.wiley.com/doi/10.1002/jor.22340/full