Presumably, if left to itself, evolution would eventually sort out these problems, but modern medical techniques probably militate against that.
Actually no, evolution wouldn't necessarily correct the problems. The way it works is that for any change to be incorporated into a genome it has to produce a positive difference in the ability for individuals to have offspring. If you can have sufficient children despite things that appear to be negatives, such as our backs, then your species can continue without having the problem corrected. After all we all have back problems, but those problem don't shorten our life spans enough to significantly affect the production of children. So there is no great reason that corrected backs would catch on from the point of natural selection.
It has been suggested that modern medicine will produce an end to evolution of the human race. However in my opinion the biggest force stopping continued evolution is the sheer mass of humanity alive. Significant evolutionary changes tend to take place more in isolated small populations. We don't have those any more. That doesn't say that we won't evolve any more. It just means that we probably won't see any significant physical changes.