Something wrong with front paw

Hi, my rabbit Lucy is holding up her front right paw. It started about a week ago. I don't think she fell or anything. She is eating, drinking, pooing and peeing. She's using her both paws to clean her face, but seems to be a little sad and doesn't want to run around as much as usual. She's not limping, just not putting weight on her right paw.
Anyway, I took her to our vet to be examined. The vet examined her, felt her leg, tried to move it in different angles and said that nothing is broken or swollen and gave us pain injection (Ketoprofen), but it didn't seem to work, so I brought her back to the vets next morning. This time they gave us anti - inflammatory drugs and same Ketoprofen. For a few days it seemed to work and she was feeling a lot better. She was putting weight on her paw and acting normally, but when we stopped those meds she started holding her paw up again.
Yesterday I took her back to the vets, they did an X - ray and it didn't show any broken bones, dislocations, arthritis (she's around 7 years old) or anything abnormal. So they gave us more anti - inflammatory meds. But this time they don't seem to work at all. I don't know what should I do next? Maybe someone here had anything similar to our case? Thanks in advance.

The vet has done all the right things but I would personally say that maybe an MRI scan may be in order or another type of scan like an ultrasound to check for tissue wastage or damage to the tendons which wouldn't show up on the X-ray.
I would go back or talk to the vets about upping her dose of the imflammatory drugs and pain relief. Ketofen is a 24hr drug so really she needs it repeating every 24 hrs to have maximum effect.