If your dog is getting up there in age, you may notice their hind legs start to weaken and cause them problems. Various factors can lead to the weakening of your pet's hind legs, especially in senior dogs. Arthritis, just like humans, dogs can get arthritis, especially in their back legs. Osteoarthritis is a type of arthritis that particularly affects the hind legs of a dog. Diabetes can cause weakness in your pet's hind legs, this happens when their body produces insufficient insulin, leading to unusual blood sugar levels, look for signs like increased thirst and hunger, incontinence, and weight loss. As dogs age, their metabolism slows down, and excess weight can cause strain, weakening their legs. Muscle mass loss and decreased walking speed in general are also signs of hind leg weakness. Sudden hind leg weakness in dogs can be caused by many reasons, including arthritis, hip dysplasia, canine degenerative myelopathy, diabetes, and fibrocartilaginous embolism.