Unfortunately, no. I have had 2 experiences with blown air sacs (which I am assuming this guy had based on your description), and both ended badly. The birds eventually died of the injury. One took a week, but one took 4 months. I thought both were healed, or at least healing well. Both died suddenly and with little warning.
Your poult is showing signs of further problems. I would process before you lose the whole bird. That's just me, though. That is based on my experience with this underlying issue. Take my opinion with a grain of salt, and do what you will with it.
You are not going to fix a badly torn ligament without a vet's intervention. If the bird can manage with the injury, then s/he may be OK. But if you deem this injury to be a game changer, then listen to your gut. A bird with a serious leg issue is not going to have a great quality of life. A minor limp is awkward, but survivable. A serious disruption in mobility that is unable to be fixed outside of surgery, is a big deal, and worth considering euthanization.
