Since the joint is made of soft cartilage until six months of age, it causes the ball and socket to flatten out. The most critical time in the development of the coxofemoral joint is from birth to 60 days of age . . . At 6 months of age, function, tissue strength, and ossification have progressed sufficiently to prevent the disease under usual circumstances. The improper fit will cause the joint to wear unevenly, which damages the smooth cartilage lining of the joint which allows smooth movement. When this natural lubricating surface is worn away, scar tissue builds up.
Many dogs show no problems until they are six to eight years old or older.
Stoic Dog A Border Collie has a very high pain tolerance. I know of several who have literally suffered broken bones while working, and kept on going. The owner was unaware of the injury until that evening or the next morning. When working, a good Border Collie is so intent on its charges that it is oblivious to all else. This means a dog could have borderline or mild hip dysplasia and still win sheepdog trials, or do a decent day's work on a smaller farm or ranch.