Swelling of the feet under the knees in front

Female 41 years old.

Hello! Trauma of the lower limbs was not. Now worries pain and swelling under the right knee, in front, closer to the inner side, pain burning, especially after a long time you sit or are. It all began about a month ago with the fact that I began to pull the lower back, then the thoracic spine was very sick and I could not normally get on my right leg, because the pain was not only on the back of the thigh, but also gave to the knee, sometimes there was a feeling that I was losing my leg while walking. I underwent a course of manual therapy, I was replaced with disks in the lumbar region, after which the back pain began to subside and gradually began to release the right leg, but not completely. The sensation of burning along the back of the thigh is still, and the swelling under the knee does not go away , and especially hurts after squatting on this leg. Pictures of the hip and knee joints did not give anything, doctors say that everything is normal, the tomography of the spine showed osteochondrosis of 4 and 5 vertebrae. That is, according to the doctors nothing serious, but I walk so normally and I can not. Tell me, please, what can it be. Is it related to the spine? What measures need to be taken? Thank you.