What would cause severe odema in the tibial epiphysis in an adult could it be an acl rupture/ knee dislocation? or can any rheumatology conditions cause it?

Osteoarthritis: By the "tibial epiphysis" I am assuming that you're referring to the proximal tibia near the knee joint. MRI changes called oedema in that area associated with pain typically occur after trauma or injury or can indicate chronic osteoarthritis. Depending on the cause, such a bone bruise can either heal in time or progress. Examination by an orthopedic surgeon can give you your specific diagnosis.