So… reading about peoples experiences at the Military Entrance Processing Station (is there nothing people won’t blog about) I’m gonna guess that it won’t be too much of a problem assuming you have the full normal range of movements with the limb and it doesn’t cause you any pain. A couple of people have said that the recruiteer may tell you not to list certain conditions as he or she doesn’t want it to hold up your processing but if it is discovered you omitted something you will be in trouble. Any surgery on the joints will probably require you submit the medical reports (discharge summary, surgeons report, x-rays etc) to the recruiter. At the actual phyisical they will get you to perfom routine movements (waving the arms, walking, jumping, crouching etc) to see if you have a full range of motion and it doesn’t cause you pain.
From the DOD list disqualifying medical conditions regarding fractures (Im guessing thats why they pinned your ankle?)
Retained hardware (733.99) (including plates, pins, rods, wires, or screws used for fixation) is not disqualifying if fractures are healed, ligaments are stable, there is no pain, and it is not subject to easy trauma. So even if the pin was there it would necessarily be a problem as long it wasn’t causing you a problem.
Also you have to remember that even if you are disqualifed on medical grounds you can get a medical waiver for anything (except seafood allergies if you want to join the coast guard – seriously is that all the US coast guard eat?) although actually getting the waiver depends on how much the service branch your applying for wants you and what the condition was.