unexplained acute pain

Question
My 2 years old female German short hair pointer (sterilised), has episode of
yelping with obvious associated pain. Recently this has been associated with
pain in back legs. Between these episodes she is fine, eats well, play and run
around as usual but the episodes are becoming more frequent. The local vet
can't explain it. What is your opinion

Answer
I don't know what it is because I can't even see the dog but it sounds like back pain to me. Sometimes they hurt their sacrums running and jumping and that will cause a yelp of pain. Other causes are knees that go in and out of joint, bad hocks and spinal pain.
Without a full set of x-rays and a workup- there is no way to tell what is wrong with her.
Take her to another vet for a second opinion.