Reminded me of my 'Rosie' who passed 3 years ago. She was born to a too young stray with too large a litter. Rosie was the last formed and had mangled, deformed hind legs as a result. Nothing could be done but she managed to get around by scooting and she lived a good, long life. Even though it was hard for her, she used a special litter box and never once had an accident.
Sadly, she developed rapid growth tumors on her mouth at around age 13 and I had to let her go peacefully. At the vets, she reached up and gave me a last kiss while I cried like a baby. I felt like she was telling me it was ok and thanking me for her rescue. I will never forget her.