If the pain is at the distal end of the long bone, it could instead be HOD, in which case a trip to the vet is certainly in order. (siriusdog.com)
It is characterized by progressive damage to the joint cartilage — the cushioning material at the end of long bones — and causes changes in the structures around the joint. (sciencedaily.com)
The cartilage found at the ends of long bones and between the spinal discs contains high percentage of water, which serves as a lubricant during the movement of the joint. (fitnessandpower.com)