Weakness in the Rear Limbs

In any giant breed dog, the inability to rise, stand, and walk is often a death sentence and disability in the rear end is the third most frequent cause of death in Irish Wolfhounds. In the past few years, we’ve made significant progress in understanding the progression of heart disease. There are clinical trials for, and improvements in, the treatment of both heart disease in our breed and in osteosarcoma. But rear end weakness, also known as “down in the rear,” is not a large part of our collective consciousness. Often, this is simply assumed to be a sign of old age. One important reason for this is that there is not one single condition, with a single cause and a single treatment protocol, associated with this problem. There are MANY conditions that can lead to weakness in the rear limbs of dogs.

The causes of this problem fall into two main groups: those in which pain prevents normal movement and those in which weakness rather than pain is the underlying issue. And while not a primary cause of the inability to ambulate well, obesity can compound each and every one of these problems. It can be the factor that takes an individual from having problems that are manageable to one who is going to be euthanized because his owner can no longer provide care.

The following is an overview of many of the causes that lead to the inability to rise, stand, and walk well:

Conditions that cause pain-

Degenerative osteoarthritis: Immune mediated arthritis is very rare in dogs, so when we refer to arthritis, we are referring to the “wear and tear” type conditions of osteoarthritis. Anyone who has personal experience with an arthritic joint can attest that this can cause a low grade constant pain, but may also cause more intense intermittent pain. It can occur in any joint, but in dogs, it most commonly affects the hips, the knees, the elbows, and to a lesser extent, the shoulders.

There are a variety of changes that occur inside an arthritic joint. Inflammation occurs in the structures inside the joint, changing and decreasing the effectiveness of the joint fluid and its ability to lubricate the joint. At the same time, inherent instability prompts the body to compensate, by laying down new tissues around the joint in an attempt to make the joint more stable, leading to the knobby appearance and feel of affected joints.

Hips- It is common to refer to all arthritis in the hips as dysplasia, but this is not technically correct. Dysplasia refers to abnormal growth or development, and in the case of hip dysplasia specifically refers to the genetic tendency to have poorly constructed joints. Dysplasia speeds the wear and tear on a joint but is really separate from the arthritis which develops. This is also true for elbow dysplasia. Dyplasia can lead to a more severe arthritis at a younger age than would develop otherwise, but not all arthritis is the result of an inherent abnormality in the joint structure. Injuries also increase the risk and severity of arthritis that later
develops in a joint.

Hip pain is a very common cause for a dog to have trouble standing and the one most often assumed by veterinarians. When the hips hurt, over time the dog bears more of his weight on the front legs by shifting the way he stands and walks. Eventually this leads to a decrease in the muscle mass of the hind legs and in increase in the muscles of the forelegs and shoulders. This may give the dog a general appearance that can remind you of a bison; very muscular in front with loss of mass in the rear half of the body.

Arthritis in the hips generally produces pain when the leg is extended behind the dog and this can be used to begin differentiate pain in this location from other pain or weakness in the rear legs. Radiographic changes may not correlate well with physical pain experienced by the dog. Some individuals have horrible looking radiographic films and relatively little pain and others exhibit great clinical pain with much less radiographic evidence of arthritis.

Elbows- Elbow dysplasia is a more common condition in our breed than has been commonly realized and can cause significant lameness in puppies as early as 5 months of age. It often occurs in both elbows, and since a dog can’t limp on both front legs at the same time, it may go unrecognized. Arthritis in the elbows eventually leads to palpably thickened and knobby joints, is commonly found in older wolfhounds, and is a significant cause of difficulty in rising.

Shoulders- Arthritis in the shoulder is most often due to a previous OCD lesion. Osteo Chondritis Dessicans leads to abnormally thick cartilage on the surface of the head of the humerus, or upper arm bone, between 4 and 7 months of age. Forces that would not damage normal articular cartilage may lead to the formation of a cartilage flap inside the joint. Early surgery to remove this flap may decrease the changes inside the joint as the dog ages, but some degree of arthritis is almost inevitable. This problem often occurs in both shoulders. Early in the course of OCD, pain can be elicited by straightening the leg and raising the foot, extending the shoulder forward.

Stifle- More commonly referred to as the knee, this is one of the most common sites of arthritis. Anterior, or Cranial, Cruciate Ligament tears, both complete and partial, cause a sudden onset of severe lameness. Injury to this structure causes the joint to be very unstable and over time leads to very obvious bony changes that are easy to feel on palpation.

Intervertebral Disc Disease (IVDD): Changes in the cartilage pads between the vertebrae, the bones of the spinal column, can lead to pressure being placed on the spinal cord itself. The earliest sign of this condition is pain, though it can lead to weakness or paralysis in some circumstances. When it occurs in the back, or lumbar spine, it may cause the dog to stand or walk with the spine arched. Muscle spasms may occur as he tries to shift and alleviate the forces causing the pain.

“Wobblers Syndrome”: Also known as cervical instability, this is an instability of the joints of the spinal column in the neck which leads to the production of both soft connective tissue and bone in an attempt to add stability. This may cause pressure on the spinal cord, causing pain and some degree of neurologic dysfunction, including weakness and balance problems. While technically affecting the front half of the dog, this condition can prevent the dog from standing and walking normally and may be confused with rear end problems.

Spondylosis: Effectively, this is arthritis of the joints of the spine, and bony changes may press on the spinal cord causing symptoms similar to IVDD even though the discs are normal.

Cauda Equina Syndrome: Also known as Lumbosacral Syndrome, this occurs when any disease process alters the spinal canal or the blood vessels in this region, resulting in damage to the end of the spine and the nerves that come off it. Signs are usually insidious and slowly progressive. The dog may exhibit difficulty in rising, reluctance to jump or play, decreased tail wagging or ataxia. As compression of nerve roots continues, the pelvic limbs often become weaker and eventually incontinence (fecal and/or urinary) may occur.

Conditions that cause weakness

These conditions generally fall into three categories: neuromuscular, cardiopulmonary, and metabolic conditions. Neuromuscular conditions can be caused by a lesion or disease process of the spinal cord, the peripheral nerves or the connection of the nerves to the muscle tissue. Neurologic symptoms are not caused by pain, but by the inability of nerve impulses to pass normally from the muscle to the brain or back. The dog may not know where its feet and legs are in relationship to the body or the ground, causing balance problems, may be unable to place the feet normally on the floor, or may be unable to recognize when its feet are placed abnormally. These are known as proprioception deficits. Abnormal nerve impulses also causes weakness, known as paresis, or, in more serious cases, paralysis, the inability to move the limbs.

Degenerative myelopathy: This is a slowly progressive degeneration of the spinal cord. Early signs include difficulty in rising or noticeable swaying in the dog’s gait. This may be confused with hip dysplasia and other causes of hindlimb weakness, however hip dysplasia is not associated with neurological deficits and DM is not associated with pain. You may hear scuffing of the toe nails of the rear feet or see dragging of the rear limbs while walking, with abnormal wear of the nails. The rear limbs may cross over each other even before obvious hindlimb weakness is seen. Progressively, the signs become more severe and eventually affect the forelegs if the dog is not euthanized. There is no effective treatment for this condition and definitive diagnosis cannot be made without post mortem testing. This has not yet definitively been diagnosed in wolfhounds.

Intervertebral Disc Disease, “Wobblers Syndrome”, and Cauda Equina Syndrome: As noted above, these conditions are often painful, but may also causes neurologic symptoms. Affected individuals usually have difficulty when trying to stand and may have proprioceptive deficits.

Neoplasia: Any tumor of the spinal cord or growth that presses on the spinal cord or brain may cause neurologic problems. These are usually slowly progressive.

Myasthenia Gravis: This is an autoimmune disease affecting the connection between the nerves and the muscle cells. The production of antibodies destroy the acetylcholine receptors on the muscles, stopping messages from reaching the muscle cells. It causes muscular weakness and excessive fatiguability and has been associated with the development of megaesophagous in adult dogs. It has been diagnosed in wolfhounds.

Cardiopulmonary conditions: those diseases of the heart or lungs that compromise the blood flow, blood pressure, heart rate, total blood volume, or amount of oxygen carried in the blood stream and reaching the muscles, can be seen clinically as a dog who is “exercise intolerant,” unable to perform normal physical activity due to the abnormal medical condition. Treatment for underlying disease may significantly improve the dog’s quality of life. These conditions may include:

Cardiomyopathy which compromises the cardiac output of blood
Arrhythmias that affect the ultimate blood flow to the body
Bradycardias (low heart rates) that decrease total cardiac output
Valvular disease that can lead to congestive heart failure and low cardiac output
Hemorrhage - from splenic tumors that can chronically decrease oxygen carrying capacity

Other disease conditions affecting the whole body: may cause general muscle weakness that can impair the dog’s ability to get around. Hypoadrenalcorticism (low levels of hormones produced by the adrenal glands, also known as Addison’s disease) causes generalized weakness, as does Hyperadrenalcorticism (high levels of adrenal hormones, also known as Cushing’s disease). Diabetes can cause weakness, though other signs such as increased urination and water intake are usually noted first.

Electrolytes imbalances can cause generalized muscle weakness. Both high and low potassium levels, as well as high and low calcium levels, can cause muscle weakness. Chronic kidney disease, some cancers, and any systemic disease that affects the acid/base balance of the body can cause this. Some nutritional deficiencies can cause significant calcium imbalances over long periods of time. And excessively low levels of vitamin D and Thiamine (Vitamin B12) can cause muscle weaknesses.

What you need to know:

It is important for us to differentiate between the causes of difficulty rising, standing, and walking. Some conditions may be preventable. Early diagnosis of other conditions may allow for the correction of the underlying problem, or slowing of the progression of disease processes. This allows a potentially longer life span, and improved quality of life.

Recognition of those conditions that have genetic components allows for breeding decisions that decrease the numbers of dogs affected. Definitive diagnosis also allows for treatment of underlying systemic diseases, possibly alleviating symptoms entirely.

If you have a dog who is having difficulties with a “weak rear”:

  • Look at its overall health and do not simply assume it has arthritis.
  • Have basic testing done to rule out the systemic problems that cause weakness.
  • Have heart and lung function evaluated.
  • Have a neurologic exam performed.
  • Try to localize and pain that may be the underlying cause.

Before your dog has any symptoms:

  • Maintain your wolfhound at a healthy weight. Any extra weight is likely to increase the severity of symptoms seen in any of the causes listed above.
  • Make an active effort, while your dog is young and healthy, to build muscle and improve cardiovascular function with regular long walks or hikes and “physical therapy” style exercise.
  • Continue to have annual cardiac screenings performed.
  • Know the difference between the signs of pain and of neurologic dysfunction.
  • If you feel your wolfhound is showing signs of “getting old,” do not assume there is no other cause. Old age is not a disease and some symptoms we attribute to aging are really signs of early chronic disease conditions.