That's more of a physical limitation that I first interpreted you as meaning. Still, I'm not going to put it in the "OMG, must be solved" category.
Feldenkrais Method (a approach of gentle repeated movements to increase physical awareness and coordination) might be a good idea. Somatics by Thomas Hanna has a daily cat stretch which takes about ten minutes to do, and as I recall, about two hours to learn.
A little extra explanation: I've found that knee and hip problems can actually be a result of a tight lower back, and Feldenkrais can help.
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.