How long should i wait to exercise if a sprained my knee?

See medical provider: A sprained knee can mean a variety of things. You should see a medical provider and get a diagnosis (MCL sprain, ACL injury, etc.) Once a firm diagnosis is made, the length of time until you can exercise can be determined. If there is any question as to what is exactly injured in your knee, an MRI can determine that.

Depends: It depends a little on the exercise. Ideally you would not do anything that would out any additional stress on the knee until you are fully recovered, and best with a gradual return. About two weeks after complete resolution of symptoms such as pain and swelling would be a good guideline. Also need to make sure strength gets equal to other side as well.