Most cases can be managed according to the RICE principles. That is.
R (rest): rest, braking the injured joint, with the use of a cast, brace etc to protect the joint.
I (ice): apply ice immediately. Ice can be applied within 24 to 72 hours after the injury to reduce swelling and pain. In the case of medial collateral ligament injuries of the knee, for example, ice should be applied for 10-20 minutes each time, repeatedly at intervals of 1 to 2 hours, 5 to 6 times on the first day, decreasing as appropriate later.
C (compression): Compression bandage, either an elastic bandage or a soft dressing plus a bandage to reduce swelling.
E (elevation): elevate the injured joint above the heart to help with the return of veins etc to reduce swelling.