Hello everybody!

Our Mastiff girl has a limp on her back paw and the vets can't give a clear diagnosis. She's 6,5 years old. A couple of months ago we noticed that she began to lean on that paw less. Then there was this day when she happily played with a Dalmatian running a lot. When she came back, she was walking on 3 paws. She's been hobbling like this for the past 2 weeks. We X-rayed her hip joint and knee joint, the vet made a couple of injections but nothing has helped. The vet didn't say exactly what's wrong with her, but looking at the X-rays he said there are "some" changes in the hip joint or maybe rupture of ligament. We're really at a loss and are very worried about our girl. If anyone can give advice, we'll be very grateful!
You say that your vet x-rayed the hip and knee, but you didn't mention the toe and ankle joints. Has that been looked at?
Actually no. The vet didn't even say anything about it. Why could he have missed it I wonder?
I can't answer why he may not have thought of checking the foot, but if nothing shows in the knee and hip x-rays, then I would ask him to look at it for you.

Something that doesn't show up on x-rays is soft tissue damage such as a pulled muscle, or a sprain. Your dog's limp could also be caused by one of those.