If the condition persists long enough, he'll have to meet a Medical Evaluation Board (aka, MEB).
The outcome of that determines whether the individual will be retained in service with a medical profile, medically separated/discharged, or medically retired. Medical retirement usually isn't a factor unless the person has well over 10 years in service, and usually closer to 15 years.
Granted this is based on Air Force knowledge, particularly a close friend of mine who got T-boned in an intersection by a cager while riding his motorcycle, resulting in his having a composite organic/metallic pelvic region, but they reassembled him and let him continue to 24 years in service.
The MEB process is pretty much standard across all branches of DoD.