Back pain is extremely complex and notoriously resistant to any kind of treatment,6probably because it is strongly influenced by many factors that we don’t understand or can’t control (like genetics, or the mind game in low back pain). In spite of this, orthotics or heels lifts are often prescribed for back pain, usually to treat a leg-length difference, which may or may not actually exist in the first place, and probably doesn’t have anything to do with the back pain.7 Back pain correlates surprisingly poorly even with the most obvious structural/degenerative issues in the spine,8 so it’s unlikely that it would be much affected by the subtler biomechanical issues that might be influenced by gait.
The evidence available on this topic — so far, such as it is, just a few small trials — suggests that insoles or foot orthoses do not prevent or treat back pain, which is hardly a surprise.9 Technically the evidence is just inadequate and inconclusive, but the absence of any benefit in the small trials done so far is damning. The only studies with positive results have obvious flaws.10
The repetitive strain injuries that runners, walkers, and hikers get are common and difficult, and they are probably the main thing that gets most people wondering if they need some orthotics. This is based on the flawed notion that RSIs are caused by flawed biomechanics.
While biomechanics may be a factor, the main problem with most repetitive strain injuries is, strangely enough, repetitive strain — that is, your body parts would likely be feeling the strain even if you were biomechanically flawless.
There can also be much more exotic factors, like the genetics of healing mechanisms, that may dwarf other factors — that is, some people will get Achilles tendinitis if they so much as go for a walk, whereas some people can run marathons for decades without any tendon trouble. These sorts of things are all explored in great detail in my free repetitive strain injury tutorial. All I want to get across here is that treating RSI is definitely not just a case of “fix those biomechanics!” It’s much harder to know if RSIs can really be treated with orthotics than you probably thought.
But it gets even worse.
A lot has to fall into place before orthotics can possibly work. Even if you do have a biomechanical glitch at the heart of your RSI:
You must have a diagnosable biomechanical problem, probably something really glaringly obvious, because anything more subtle and you’ll probably get different diagnoses from different professionals.
The diagnosed problem must be relevant to your injury. This usually has to be a shot in the dark, because most RSIs are not clearly associated with any known biomechanical problem.
The problem must then be correctable at least in principle. Quite a few problems simply cannot be fixed by orthotics. It depends on the problem.
Assuming all of the above work out, you will still need to get the correct prescription, properly made.
If you can’t tick off one of those, the game is up: orthotics aren’t going to work out. It all adds up to a very long shot, which is probably why evidence about the efficacy of orthotics for treating any lower limb problems has been discouraging.11 Evidence
And yet orthotics could still be worth trying — particularly if you do have a fairly obvious biomechanical problem. Good orthotics are a reasonably good way of trying to “tinker” with any gait or postural dysfunction that may have contributed to your pain in the first place. For instance, unusually high arches are a plausible factor in runner’s knee.