I had a similar problem when I was a child. Though I did not fall while walking, I was severely bowlegged, and eventually needed surgery because of knee pain. You need to find the underlying cause of the distortion to the bones. In my case, I had childhood ricketts, now adult osteomalacia. It is a vitamin D deficiency. My nephew also has the condition, and aslo had surgery to correct his bowleggedness. For myself it was an intense surgery. I was 12 years old, and had to have an tibial osteotomy. Basically, they broke and reset my tibia (lower bone in leg). A small metal plate and screws were used to reset the bone, and I had to wear a cast for some time. This sounds scary, but it is just like a child breaking a bone, and needing a cast for a few weeks. What was so horrible about it is that I was 12, and I had both legs corrected at the same time. Being in 2 full leg casts, needing a wheel chair to get around is not easy for a preteen. I had to return to the op room to have the screws removed a couple years later, when the docs were sure my bones were strong enough. That part was not so bad.
My nephew who has the same condition, had a different type of surgery done last year. Since he was only 4, the doctors took a different approach. They somehow restricted the growth plate on his tibia. The restriction is to prevent the bone to grow in a curved way (bow). I don't know exact details of how (sorry). However, it was a about a 3 hour process, one night in the hospital, and he was walking again within a week. Now after a year, his legs look very different- straight. The doctor plans to remove any hardware and free the growth plate in a couple years. My nephew no longer complains of knee pain or having really tired legs. And it seems like he is growing so tall suddenly.
I don't know if the surgeries were different because of our ages, or because technology has advanced, but my guess is with a younger child the doctor would choose to go with the latter.
Both my nephew and I were seen at Boston Children's Hospital. Make the drive; I highly recommend seeking one of their orthopedic surgeons, I saw Dr. James Kasser. I believe he is head of orthopedics now. Not only are they more willing to research newer ideas & methods, but they are more understanding about scared kids.
Good Luck!