Most lower back conditions develop from bending over to lift, which causes the joints in your lower back to be at their most unstable point. In this position, the joints are not locked into position tightly as when lifting with back straight and knees bent. The way to determine that nature of your condition and its correction is through proper examination. Chiropractic helps many conditions. Many people seek out chiropractic first, as opposed to last as in your case.
Most knee injuries occur from bending and twisting the knee at the same time.
This is when the knee is also at its most unstable point. Ligaments, cartilage and other structures are torqued and twisted unnaturally. I had a football player from the Atlanta Falcons in recently for a knee injury. Compared to the back, the knee is actually a very simple structure. There are certain positions and angles that it may be placed into which makes it very unstable and easily injured.