I don't know what they qualifications are now but back in the day (damn that sounds old), asthma would DQ you. Flat feet. An assortment of injuries; especially, to joints that required surgery. HIV would do it. Being married
The US government doesn't want to pay to fix you with no guarantee you'll be worth the fix. Especially given the benefits associated with service-related injuries. If they accept you, it is automatically a service related injury unless they can prove fraudulent enlistment.
This would be taking a chance at the unknown or possible residual effects.