I don't know anything about dogs with torn CLs, but know a bit about people with 'em...could be similar, but could be very different. In people with torn Anterior CLs (ACL), most orthos try a conservative route first to see if the tear will heal itself with out surgery. Since the ACL has a decent blood supply, and that's what's needed for it to heal/repair, steroids along with a month of zero pressure on the area i.e. NO walking or weight-bearing, may do the trick. Since no further damage will be done by delaying surgery, this is definitely a great option for folks who can live on crutches for 6 weeks. After the ACL is repaired, either surgically or by rest, a few months of physical therapy is prescribed.
OTOH, tears to the MCL have little to no chance of repairing themselves with out surgery because of the very, very small blood supply to that ligament. Surgery is the standard protocol for torn MCLs, followed by physical therapy.
My daughter had a torn ACL. We followed the docs advice and had her hobble around on crutches for 6 weeks followed by 3 months of physical therapy. The only thing she can't do is the required kick for breast stroke...and she's a competitive swimmer and her best stroke is...you guessed it, breast stroke. But since this is her last year to compete, I don't regret the decision to avoid surgery. She was able to regain her activity level with out surgery.