What to think about
Depending on how bad your injury is, surgery with rehab may offer the best chance of making your knee stable again. It also may help you return to an active lifestyle without further pain, injury, or loss of strength and movement in your knee.
If your injured knee gives out now and then (chronic ACL deficiency) and you continue to do activities that require a stable knee, you may injure your knee again. That may be another reason to consider surgery.
You will need to follow a rehab program whether or not you have surgery. If you don't complete a rehab program, even with surgery you may not regain full stability and function in your knee.
Source: http://www.webmd.com