Lateral foot wedging is being used increasingly to treat medial knee osteoarthritis. There is plenty of literature on it. I just want to add these observations:
- Several national rheumatology organizations recommend them in their guidelines, so there is no excuse for not know about them
They work up decreasing the knee adduction moment (which, along with a high BMI, are the major risk factors for medial knee osteoarthritis)
- Wedges to need to be full length to get the desired effect (see this research). This is probably the case becasue, that if the wedge goes under the lateral forefoot, it has a large lever arm to the subtalar joint, so is likely to be more effective. However, a good lever arm will still be obtained from just a heel wedge if the subtalar joint axis is more medially located.
- The foot is not at increased risk for developing foot problems despite being in a more pronated position (those who have been to the Boot Camp know my arguments there)
- I believe that those with more limited subtalar joint eversion or a more rigid foot are more likely to benefit from lateral wedging. If the foot is more mobile, the effect of the wedge is probably ‘absorbed’ in the foot. If the foot is more rigid, the moments are probably changes further up the leg.
- Shoe fit has never been a problem. Those with medial knee OA are happy to wear runners to accommodate the wedges.
Most of the studies have shown mixed results, but this is possible due to:
- The wedges used were not full length. Most studies do not adequately describe the wedge they used.
- Those with a high BMI being included in the studies (the OA will probably progress in these cases regardless)
- There are several large RCT’s underway at the moment doing more definitive testing on lateral wedges.
The most recent information is on this thread at Podiatry Arena: Lateral wedging for medial knee osteoarthritis.