My dog tore both of his CCLs. That is actually very common... if a dog tears one there is at least a 50% chance he will also tear the other at some point in his life.
I really did not want to put him through the surgery and months of recovery but after researching it and talking to several vets I learned that surgery is the best long term option. Without the repair the dog will have lifelong pain and degeneration of the joint due to instability. So, when he tore his first we opted for the "fishing line" surgery, which is the oldest and most commonly performed. It took him months to recover and there was quite a bit of pain involved. When he tore his other CCL we found a surgeon who performed TPLO surgery. This surgery does not introduce a surrogate ligament; instead, the tibial plate is reshaped to allow for smooth interaction. The difference in recovery time and pain is STRIKING. With TPLO a dog is back to normal much faster and with far less discomfort. I really wish I had gone with TPLO for his first. The only drawbacks with TPLO are finding a vet surgeon with the equipment and expertise to do it, and of course, the cost. TPLO can run around $4000 but to me it was well worth it.