Yes it could be related to her joint ill. There are also arthritic conditons they can get, at least some of which are caused by diseases carried by ticks.
First off, though, if you haven't already, check between her toes for any wet broken skin, likely to be scald, which can also make them walk stiffly. If you see anything other than dry, cool, intact flesh between the toes, a spray of terramycin will make her feel a lot better.
If no scald, your vet will know what are the most likely bugs in your area and hence should be able to advise what antibiotic to use.