How should I treat a dislocated knee?

Orthopaedic Surgeon! A true knee joint dislocation can be an orthopaedic emergency. A patella dislocation is much less serious and, once reduced, not an emergency. A visit to an er is warranted for a knee dislocation. Appropriate initial emergency care and evaluation of nerve function and vascular integrity is mandated to avoid catastrophic loss of limb. Orthopaedic care likely involves major reconstructive surgery.
Very complicated. A true knee dislocation involves multiple major knee ligament ruptures. It requires expert and extensive surgery. Make sure you aren't confusing a knee dislocation with a patella dislocation. That condition is entirely different.