Panosteitis

Also known as 'long bone disease', 'wandering lameness', or 'pano'. Most commonly seen between the ages of 5 to 12 months, and for unknown reasons, is common in the German Shepherd breed. Pano is caused by excessive bone production on the long bones. Normally, a dog affected by this condition will grow out of the problem, but it is painful.

Diet is thought to be a contributing factor in the development of Pano. High protein puppy diets may make the puppy grow too fast and increase the chance of the pup experiencing Pano which is also sometimes described as "growing pains." Pano can also show up in any leg and may come and go without warning. Puppies usually completely outgrow Pano by the age of 18 months and it rarely goes beyond two years.

Full information can be found at this link Pet Education - Panosteitis.