How do I treat knee hyperextension until I can get in to see the orthodoc?

RICE therapy. The pneumonic r.I.C.E. Helps guide the general treatment of orthopedic injuries until a more thorough eval can be done. It stands for rest, ice, compression, and elevation. In addition, tylenol (acetaminophen) and anti-inflammatories can help with the pain. If it hurts to put weight on it, don't. Get some crutches and stay off of it. A brace or immobilizer can help relieve pain as well.