Read this link on vitamin c and Hip Dysplasia:
http://www.neapolitanworld.com/health2.htm
Then also read this....

Vitamin C

A deficiency in vitamin C is a deficiency in the healing, glandular, circulatory, immune, and regenerative abilities of the body. Vitamin C is a major factor in the formation and maintenance of bones and tissues, prevents cancer, and may prevent arteriosclerosis.
The classic vitamin C deficiency is scurvy, with gum disease, loss of teeth, weakened bones, bleeding, bad breath, and general debilitation. Signs of clinical scurvy have been apparent under stress.
In dogs, [vitamin C] can totally resolve the problems of dysplastic hips in younger dogs and arthritis in older ones, as well as help or cure spinal myelopathy, ruptured discs, allergies, viral infections (including distemper), and skin problems. After the "cures," the pet needs to stay on C, but in lesser amounts.
The vitamin is an antioxidant, a pollution fighter that cleans toxins from the blood and tissues.
It helps protect against the side-effects of some veterinary drugs (including steroids/cortisone), and it is a major pain reliever.
It keeps the teeth strong in aging pets and retards the aging process.
Supplementing with vitamin C is a major disease preventive; therefore it's emphasized in the daily feeding plans.
Supplementing with vitamin C can mean the difference between life and death in the case of a sick cat or dog.
Contrary to myth and rumor, vitamin C will not cause kidney stones, it dissolves them.

I recommend when pups start limping to bring them up to tolerance with Ester C by increasing in 500mg increments each day. When they start getting loose stools back off the dosage of the day before and stay there. This is all explained in the above link. We buy human grade Ester C. We get 100 1000mg tablets at Walmart for 14.98 the brand is Spring Valley.