So sorry to hear this about Lily. This happened to (RB) Tonee too. Her's was torn when jumping 'up' on the bed one night . I heard it happen, well, the yelp any way, not the tear. To make a long long long (this is also when she was diagnosed with Cushings )story short, she was too old for surgery too. The vet put a 'sort of' splint on it. And she recovered rather well. Same as with people, you don't always 'have' to have surgery to make it better.
Katz