Hip dysplasia does not cause urinary incontinence. Hip dysplasia is an abnormal forming of the hip joint, so the ball and socket joint. The joint that connects the pelvis to the long bone of the back leg. That causes arthritis in that joint and it can cause a dog to be stiff and to have pain and difficulty getting around. It does not cause urinary incontinence in dogs at all.
Now, sometimes dogs with hip dysplasia, they will also have another condition called lumbosacral stenosis, or Cauda Equina Syndrome, where the ventral canal, the spinal column, is narrower than it should be due to arthritic changes in the spine. That can cause incontinence. So, if you have a dog with hip dysplasia that is also incontinent, then you likely have more than one problem going on there and you need to get some more testing from your vet.
Sometimes dogs can be so painful, or it can be so difficult for them to get up that they may just urinate where they’re at because it’s too difficult for them to get up and get outside to go the bathroom. That is a problem with pain and arthritis in the hip joints. That’s not incontinence, that is, it hurts too much to get up. In those cases, you may want to talk to your veterinarian about different ways to help your dog be more mobile and in less pain and maybe look into getting some sort of diaper for your dog until you get the hip dysplasia under control.