One explanation may be this: with canine hip dysplasia, there may be muscle wasting in the hind legs, which explains the trembling that your dog experiences in the hind legs. Canine hip dysplasia is a developmental orthopedic disease in which an abnormal formation of the hip leads to looseness in the hip joints, causing cartilage damage. Progressive arthritis can result, and when it does, it can be crippling. Hip dysplasia is not the same thing as arthritis in the hips rather, it is the most common cause of arthritis in the hips.Hip dysplasia is most common among larger breeds of dogs, especially German shepherds, rotweillers, Labrador retrievers, golden retrievers, mastiffs, and Saint Bernards. It can also be seen in smaller breeds such as the cocker spaniel and the springer spaniel; mixed breeds may suffer from it as well. Clinical Signs: Decreased activity; difficulty rising; rear limb lameness; reluctance to use stairs, particularly to go up; reluctance to jump or stand on hind limbs; swaggering gait; bunny-hopping gait; pain from manipulation of the hip(s); decreased range-of-motion in the hips; crepitus in the hip joint; positive Ortolani sign; positive Barden’s maneuver; subluxation or complete luxation. Symptoms: Less energy and movement; difficulty rising; lameness in the back legs; reluctance to use stairs (particularly to go up); reluctance to jump or stand on hind limbs; swaggering gait, bunny-hopping gait; soreness after lying down; soreness after heavy exercise. [from http://www.workingdogs.com/vchipdysplasia.htm] "The symptoms of the more recent problems with the rear legs sound like a neurologic disorder. The most likely diagnoses are degenerative myelopathy, a spinal tumor or a herniated disc in the spine. Degenerative myelopathy (DM) is a progressive disease of the spinal cord in older dogs. The breeds most commonly affected include German Shepherds, Welsh Corgis, Irish Setters, and Chesapeake Bay Retrievers. The disease has an insidious onset typically around 9-11 years of age. It begins with ataxia: a loss of coordination in the hind limbs. The affected dog will wobble when walking, knuckle over or drag their feet, and may cross the feet. As the disease progresses, the limbs become weak and the dog begins to buckle at the knees and have difficulty standing. The weakness gets progressively worse until the dog is unable to walk. They may ultimately lose continence and function in the front limbs. [from http://www.vetinfo4dogs.com/dmotion.html#Problem%20with%20rear%20legs and http://www.cvm.missouri.edu/dm/#how_dx] I hope your dog turns out okay!

I know it's been a couple of years since you posted this, but my Great Dane is having the exact same thing with his back left leg. I just wondered if you ever figured out what it is? I've taken him to 4 different vets and no one knows what it is! He's had x-rays and all the tests for ACL problems. He doesn't have hip dysplasia or an ACL problem. Any info you have would be wonderful!

Hi - something very similar to that happened to my dog about 6 or 7 months ago. There have been several things that have gone on since - possibly all related to the leg shaking, possibly not - but I'll tell you just in case. At first, her neurologist felt it was likely just 'senile tremors' and not a problem (or part that and partly due to an old disc injury). A couple months later, he found she had an inner back thigh injury (near her groin area) Maybe the pain was previously causing the shaking. (she had also some time ago been on pred. and had some muscle wasting - don't know if that could have contributed to the shaking - just had to add that). Anyway - shaking subsided mostly but now has terrible muscle weakness - mostly (close to only really) after exercise - vet thought degenerative myelapothy (awful) but neuro thought not that it's myasthenia gravis - and have bee treating for that - was responding but past few days not so well. (also said could be some other neuormuscular junction problem) so point being - watch to see if it progresses to any of these things - AND you mentioned 4 different vets - but have you been to any specialists?? (like a neurolgist)? might be worth trying good luck hope this helped and hope it's nothing serious

my dane's hind leg also tremble occasionally - it does not seem to bother him but now it seems to be getting worse - i just used to notice when he was laying down that it looked like the muscles in his hind legs were "twitching" but now i am noticing it when he stands there as well. i am very concerned - any idea what this might be ( he has been OFA cert good and has no hip problems )