The muscles in the thigh are collectively called the Quadracep muscles and collectively they extend the knee. During the stance phase of gait, the quadraceps also keep the knee from buckling. Sounds like your knees buckled. The force may have stretched or even partially torn a muscle. In the process of falling, the low back also took a hit. Now with weak thigh muscles and an injured back, life is really tough.

The legs and buttocks provide the base of support for the back. Without support, the back suffers even more during many activities like walking, lifting, and getting out of a chair.

Fortunately, time will heal. But you may want to be examined to make sure the weakness is indeed from a muscle injury and not something more sinister. The initial buckling of the knees may have been a product of pathological weakness from nerve damage. Sometimes falls are not so innnocent and actually signs of something more serious.

Dr. Christina Lasich, MD