Intermittent muscle weakness causing collapse

Question
On two separate occasions, I've seen my dog (Shepherd mix)get shakey weak legs and will just fall to the ground. He recovers very quickly after the event. I'm sure its happened before when I was not around so it is not likely an isolated incident. Clint, my dog, is approx 7-8 yrs and is a shelter dog so not sure of exact age. I've also noticed obsessive licking of his front left paw and even had a vet check it out with no signs of skin allergy or other ailment. not sure if this is related. I'm most concerned about his collapses due to the leg shakeyness muscle weakness. any thoughts on what to look for as a cause. Thanks, Charles (biggest dog and animal lover ever)

Answer
Charles -


I cannot attempt to diagnose without the benefit of a physical exam.  There are several diseases that can cause muscle weakness.  Arthritis, myasthenia gravis, Addison's disease, Cushings - all can cause intermittent weakness in the legs at some point during the course of the disease.  One can reach a definitive diagnosis using the history and physical exam; your vet should request testing to rule out certain diseases.

Your veterinarian can evaluate your dog and determine the cause of his muscle weakness.