A dog's leg may shake because of nerve responses, according to MentalFloss.com. This is known as the "scratch reflex," occurring when an owner playfully rubs a dog's belly. The nerves register the touch as irritation, sparking an involuntary movement of the legs. It is an instant reflex to scratch itchy areas of the body.Continue Reading
MentalFloss.com also notes that it is a healthy reaction in dogs and a testing method veterinarians use to find out if the nervous system is healthy.
BigSiteOfAmazingFacts.com notes the various theories stemming from this biological reaction, such as scaring away predators, or to safeguard dogs against drowning.
A more serious reason can be traced to kidney disease, according to MyTCMVet.com. Kidney disease can cause low electrolyte levels and mineral deficiencies, resulting in muscle dysfunction. Adrenal problems can also be related to mineral and electrolyte imbalances. General muscle weakness can also stem from arthritis or any joint-related ailment.
VetStreet.com also touches on general muscle weakness, but adds fatigue as a possible cause. A dog's leg may shake after overexerting the limbs. Pain may also be a factor, particularly within the back or abdominal regions. Stress and general anxiety may also play a role, along with medications the animal may be taking.Learn more about Dogs
Dogs kick their back legs when being rubbed and tickled because of an involuntary reaction called the scratch reflex. It is caused by nerves in the dog's stomach reacting to the tickling in an effort to get rid of an irritation.Full Answer >
Macadamia nuts pose the risk of toxicity in dogs, causing symptoms of muscle weakness of the hind legs, fever, and pain accompanied by tremors, according to the American Society for the Prevention of Cruelty to Animals. Signs of toxicosis typically last for about 48 hours.Full Answer >
When you scratch a dog on its belly, it will kick or shake its legs due to a scratch reflex. This reflex is a completely involuntary reaction.Full Answer >
The most common cause of a dog's back legs giving out is a herniated or ruptured intervertebral disc, according to the College of Veterinary Medicine at University of Missouri. A condition known as degenerative myelopathy, a slow, progressive disorder that affects the spine in older dogs, also causes weakness and paralysis.Full Answer >