I think that orphan lambs are a nightmare---often they miss out on colostrum or have been abandoned because they are weakly trips or have some other problem that is not visible (heart condition, slightly deformed somewhere?)
Later on these things show up, quite often this occurs when the weather turns a bit or when the grass looses it's goodness ----so yes, joint ill can show up later in life though it's likely the lamb has had an underlying problem for a while
It should get over it and then put the thing in the freezer asap (which is where all orphan lambs belong)