It is not the same as a dislocated kneecap
Dislocation of the knee is a rare condition, and quite different from dislocation of the kneecap. Blood vessels and nerves are at extreme risk and it is generally considered extremely important to order an angiogram as early as possible after reduction to check the arterial supply. Soft tissue damage, eg ligaments, are likely to require surgery once the situation is stable.
Structures involved in knee dislocation
The damage may involve the capsule, one or more of the cruciate and collateral ligaments, the menisci, the popliteus tendon and the blood and nerve supply. The priority is to re-establish blood supply and then stabilise the joint while the other structures are assessed.