Well, I had a similar problem many years ago and tried a lot of things. I started with the usual medical route but that led nowhere and then tried acupuncture/moxibustion, Spinal Network Analysis, etc. None of these worked so I went back to what I knew---Hatha Yoga. I was very careful what poses I did even to the point of rejecting poses that teachers thought may help but I felt discomfort in. I found that most standing poses were fine and so then I started a dedicated personal practice of a set of standing poses daily. In three odd months my problem had gone. Of course, YMMV, but I gained a lot in the process especially body awareness, good posture, etc. However, this required a fair bit of tenacity on my part and that is one caveat to this method but if you have a long term issue it is definitely worth a shot.