JunkyII,
You've had some excellent advice given to you in this thread and I am going to add a bit of spice to it because I was actually a USMC Recruiter during the post Viet Nam era from 1976-1979 and I can tell you from personal experience that Recruiting Duty is the toughest duty you will ever pull in Military Service, apart from actual combat!
Why...it's because it's like you're in combat every single day and every single thing you do, or say, will be subject to scrutiny by the public. You will have few, if any days off. You will eat, sleep, drink, breathe, and talk nothing but Army, day in, and day out. If you say something that offends someone, even though they mistook your meaning or intention, it is bad press, and bad press is bad for Army Recruiting, and you will be held responsible by your Command. If you are married, you will seldom see your wife, and it is a sad statistic that an extremely large percentage of the marriages of recruiters end in divorce due to the huge time commitment a recruiter must make away from his family.
You will have an enlistment and shipment quota to meet each month. If you fail to meet quota, you fail to make Mission! If you fail to make quota often enough your career may suffer. On the other hand, if you are so desperate to make quota and you fail to follow proper screening and enlistment procedures and actually fraud someone into the Army for the sake of making quota, I guarantee you your career will suffer! You may even spend some time in jail! Back when I was recruiting our service number was tied to each recruit we enlisted for the duration of that recruit's enlistment. So, not only were the number of recruits enlisted tracked, but the quality of the recruit enlisted was tracked! What that meant was, if you showed a pattern of enlisting substandard recruits your career would definitely not be having many more good days.
Recruiting Duty is a sales position. Think about this statement a bit because this is the crux of recruiting. What you are actually selling a potential enlistee is (unless the military obligation has changed since I enlisted), six years of his/her life, with (x) years on active duty (during which time he/she may encounter combat and be killed) and the remainder to be served in active, or inactive reserve. Since you are on active duty, you bought this line...can you sell it day in and day out, 24 hours a day, seven days a week for several years? And just one other thing to mention...Recruiting Duty will teach you to learn more about the Army and it's opportunities (because that is also what you are selling) so it may help you further your career by opening your eyes to other fields within the Army.
My advice to you at age 25 (I was 25 my first year of Recruiting Duty) is this: if you are not going to stay in the Army for the full 20, then get out now, before recruiting school, if possible, and use what G.I. benefits you have to get schooling, or learn a trade. If you are going to make the Army a career, then embrace Recruiting Duty and move forward and don't look back!
As for your knee...pay the out of pocket expense to get a civilian opinion and compare it to the opinion the Army gives you. Not knowing your circumstance I cannot advise you further on this issue. I will, however, mention that I was raised in the Army and that the Army provided me with all of my medical care as a youth until my father retired in 1962, but then resumed it's responsibility to me when I enlisted in the Army in 1968 (I had two periods of service in two branches). During my tenure under Army Medical Care I was stitched up 5 times, had 3 broken bones repaired, suffered through all of the normal childhood diseases and suffered through all of the childhood and adult inoculations. In 1957 I was administered an experimental Rabies Vaccine for a dog bite while we were station in France. Did you know that the Rabies Virus is more lethal than the Ebola Virus? I survived the inoculation. The dog that bit me did not survive. The Army had given my parents a choice between me dieing of the Rabies Virus, or me dieing from the Rabies Vaccine. Mom had been an Army Nurse in WWII where she met Dad who was recovering from wounds after three years of combat in the Pacific...they trusted Army Medical Care.
You have a lot to think about. Take some time and talk seriously with your Army Career Planer and make your knee issue known (he's probably a former Recruiter and he has a quota also, so be alert to sales techniques). Most importantly, don't give up on what you really want.
OH! Just as an aside...I failed to mention another Recruiting statistic: almost 90% of single Recruiters end their tours married! DOH!