What to do about my poor dog?

I brought my dog twice to the vet. She is diagnosed with a torn ligament with her knee. He gave her a cortisone shot and I put her on prednisone pills for 2 weeks. She still limps. Although, she does not show sign of pain. But she can't run around like she used to and she's not as perky. I can't afford surgery at this moment. I heard that you can give a dog glucosamine and it helps. she's about 12 lbs. how much should I give her if I do give her some? I just want her back to her self. she's only 6. and she still wants to run around. Please help.