<Li> Labradors are somewhat prone to hip and elbow dysplasia, especially the larger dogs, though not as much as some other breeds . Hip scores are recommended before breeding and often joint supplements are recommended . </Li> <Li> Labradors also suffer from the risk of knee problems . A luxating patella is a common occurrence in the knee where the knee dislocates and goes back into place . </Li> <Li> Eye problems are also possible in some Labradors, particularly progressive retinal atrophy, cataracts, corneal dystrophy and retinal dysplasia . Dogs which are intended to be bred should be examined by a veterinary ophthalmologist for an eye score . </Li> <Li> Hereditary myopathy, a rare inherited disorder that causes a deficiency in type II muscle fibre . Symptoms include a short stilted gait or "bunny hopping," and in rare cases ventroflexion of the neck accompanied by a kyphotic posture . </Li>

How many different types of labrador retrievers are there