Anters,
I had a hip surgery when I was 12-13, including a pin which is still present. This is what the Navy calls retained hardware. Before college, I had an ROTC scholarship, and the Army wanted me for the instant Warrant Officer Program. Both these groups told me I would have to be less than honest about my leg to get in. I was unwilling to start a military career with a lie, so I put myself through college. Just before I graduated, something clicked and I decided I was going into the Navy come hell or high water. That's when I first learned the magic of the waiver. It wasn't easy, but I had a patient recruiter, and I eventually got it. Essentially, the military has an overall idea of what physical performance their people need to be capable of, and they base physical requirements on meeting those capabilities. USUALLY, if you can prove your "defect" won't hinder those needs, a waiver will be recommended. In my case, my surgeon sent in X-rays and wrote a letter stating I had no physical impairment, and that the joint wasn't weakened by the pin. I'm including a link to the Navy Aerospace Medicine Institute waiver guide.
http://www.nomi.med.navy.mil/Text/NAMI/WaiverGuideTopics/default.htm
Remember, this is for pilot/NFOs, and is somewhat more strict than many other Navy communities with regard to physical standards. Just be honest when you fill out paperwork, and make sure you have as much documentation about your surgery as possible, they'll want to see it.
Penguin