I have an ACL (anterior cruciate ligament) tear, which was confirmed by an MRI (it my be partial or complete; I was not told which.)
My question: is surgery the only way to treat ACL tears? Is surgery necessary in order to regain full strength/function of the knee?
I an very active and would like to return to sports like skiing,
Though most people do get surgery to reconstruct their torn ACL, it is possible to regain full ability of your knee without surgery. Just through rehabilitation, you can totally recover from a torn ACL.
In a clinical trial done in 2010,1 two different treatment strategies were given to 121 young, active adults (ages 18-35) who suffered acute ACL injuries. One strategy was rehabilitation with early ACL reconstruction surgery. Most people given this treatment strategy opted for the early surgery (61 out 62). The other strategy was rehabilitation with delayed ACL reconstruction surgery. Of the 59 people treated with this strategy, only 26 people opted to get surgery. The other 36 were healed with just rehabilitation.
Though that trial was meant to find the most effective treatment of torn ACLs, it did display that with physical therapy and time, it is possible to completely recover from a major ACL injury.
There are some situations in which rehabilitation without surgical reconstruction is not very effective for a torn ACL. If other parts of the knee, such as other ligaments, have also been injured, it is recommended that you get surgery. It is also recommended that you get surgery if you are still active, as running, jumping, pivoting, and other activities that give you a higher chance of reinjuring your ACL.
1: A Randomized Trial of Treatment for Acute Anterior Cruciate Ligament Tears
Short answer, yes it is possible to have a full recovery without surgery. If the ligament is only torn, it may heal with a careful recovery plan. If it is torn, most of the strategies revolve around strengthening the muscles that also help stabilize the knee.
Most of the links that I would use were already covered in michaelpri's answer, so I would just add a bit. The function of the ACL is to keep the distal (lower) end of the femur from "sliding" off the front of the tibia, and to provide rotational stability.
Considering the position of skiing with the knees bent, and weight forward, and the rotation needed in the lower legs for turning (especially if you are a more advanced/mogul style skiier), I would highly recommend you explore the surgical option. In my opinion (And that of the AAOS), that would give you the best chance to reurn to full activity. In addition, there may be other collateral damage to the meniscus and other structures that could be repaired with surgery.
As an aside, I faced the same decision with a complete rupture of the achilles tendon, and opted for surgery. I'm back at full activity, with no after effects.
