I would try to look for the possible reasons for this condition, which may range from genetic (beejadosha) to wrong diet and behavior during pregnancy. I think it less likely that this is induced by some injury during cesarian delivery, because with cesarian, you have plenty of room to deliver the baby. My wife had a similar case with ankle dysplasia which was treated internally by various medicines, but mainly with those to improve asthi-dhatu, and externally with muruvenna tailam. This gave excellent results and now the kid is 4-5 years old and she can walk (with a limp, but far improved).

In a case like yours, possibly the ligaments are underdeveloped or are weak. Assuming this as initial working hypothesis, you may use any oil mentioned in ashtibhagna (fracture), eg,, lakshadi tailam, Muruvenna tailam, etc. Brace seems a good suggestion, which would allow some time for the tissue to develop. Use of brace is in line with the ayurvedic treatment of such condition.

If this is indeed developmental, then it means the ligaments are not formed normally right from the beginning during the pregnancy period. Formation and regeneration of new tissue is said to be function of shukra dhatu and one may think of using medications to improve shukra such as ashvagandha tailam, shatavari tailam, etc. There may be some other aspects to this particular case such as possibility of stanyadosha (impure maternal breast milk), parigarbhic vyadhi, etc., which may be taken into consideration before deciding treatment regimen.