I was able to join, in 1988, after asignificant knee injury. I provided my enlistment office with copies of ALL of my medical documentation when I signed up. I passed my medical, went to the proceesing center in Boise ID, and then to the reception station at Ft. Benning. After several weeks of training, my knee began to act up and finally my Drill Sgt. made me go to sick call. After several Drs., I was told that;
1. I should have never been allowed to join in the first place.
2. That I probably was guilty of fradulent enlistment, this carries a hefty felony penalty.
3. That the only way I could stay in the military was to become a truck driver or desk warrior.
Faced with all of this, I called my Dad and he overnighted the originals of my medical documents. I presented these to 'the brass' involved and was quickly and quietly removed from the Army and given a Medical discharge. A kindly Major told me that it was a pretty even trade, they don't prosecute the fradulent enlistment charge and I don't scream and kick wanting the enlistment Sgt. busted to Pvt1 and sent to Alaska. I also didn't get any VA or other medical benefits. It kinda pissed me off, I wanted to serve, but in combat arms. I wish the Sgt. at the enlistment would have been honest with me. He even went so far as to get me Ranger Indoctrination Program guaranteed upon enlistment....after I gave him all of my information on my bad knee.
Long story just a bit longer.... I have since had 2 ACL's blown, one in each knee and have had a total of 6 knee surgeries. If you can avoid surgery and have a full recovery, do it. Even with surgery, I am officially 9% disabled in both knees. My knees are only weak when I put them in a strange position. With everyday use, you should see no problems, but if you begin to stress them they WILL fail.
BTW, my little brother joined in 1994 and when he was in line for his physical, a guy told the Docs about a knee injury and was asked to leave and was not allowed to join. This was the Army.