Okay. Hatchery chicks. That might have strengthened my hunch that she may have the leucosis virus. Her lame leg and the way it's presenting is one of the early signs of the virus. Or it could be an injury. Or it could be a riboflavin deficiency. Time will tell.
An injury will heal. The leucosis...
Age of the chicken is necessary for us to know. So is your location, as we may be suggesting treatments you may or may not be able to obtain.
Size of your flock, free ranged or kept penned. How large is your run. All important information for us to know so we have the big picture.
The symptoms...