Posted: July 11, 2012, 6:25 p.m. EDT
© Kevin Wright, DVM, DABVP
A pet like this rabbit with arthritis or back pain might be unable to clean its own bottom anymore.
Arthritis and other degenerative joint diseases are the bane of aging small mammals everywhere. Arthritis and back disorders are widely recognized and treated in longer-lived species, such as rabbits, chinchillas, guinea pigs and ferrets. However, rats and other small mammals also develop arthritis and back disorders as they age. In all species, the signs of these conditions may be subtle and overlooked. Owners may not seek treatment because they don’t understand that their pets’ behavioral changes are responses to painful conditions. Advances in veterinary care offer hope for small mammals suffering from painful arthritis and back disorders.
What Is Arthritis?
Before you understand arthritis, you have to understand the anatomy of a joint. A joint is a flexible connection between two bones, such as the hip, knee, ankle and toes or shoulder, elbow, wrist and fingers. There are joints in the jaws and between the vertebrae (neck, back and tail bones).
A joint is lined with cartilage, a smooth, dense, flexible substance. It is filled with synovial fluid; a thick, slippery substance that keeps the cartilage lubricated so that the joint moves easily with little friction. A pouch, known as the synovial membrane, surrounds the joint and contains the synovial fluid and produces the synovial fluid. A joint, such as the knee joint, may also have a cushion known as meniscus (menisci is the plural).
All of these parts work together to keep a joint moving in a smooth and painless fashion. The efficiency of this system means that our pets generally aren’t aware of all their joints unless there is a problem with them.
As an animal ages, its joints suffer wear-and-tear. The cartilage may become pitted and rough, making the joint harder to move. The synovial fluid may become watery, providing less support for the cartilage so that the cartilage grinds together. Over time, the cartilage may wear down to the bone. Chips of cartilage may come off and float in the joint fluid, further injuring the cartilage and pouch. Damaged cartilage and synovial membranes release chemicals that cause inflammation, and the joint may be red, swollen and painful. Inflammation often interferes with joint healing, and a vicious cycle starts of cartilage destruction, bone grinding and pouch irritation.
What Are Back Disorders?
As mentioned above, there are joints between the vertebrae. An important function of the vertebrae is to protect the spinal cord that runs from the brain to the tail. If the spinal cord is injured, it may result in temporary or permanent paralysis, depending on the kind of injury. As a result, the vertebrae have limited range-of-motion so they do not kink the spinal cord. The vertebrae are prevented from flexing too far in any direction by a series of bony protuberances linking one vertebra to the next one, some ligaments that strengthen the bond between vertebrae, and the menisci (also known as intervertebral discs) inside the joints.
The back is very sensitive to arthritis. Often the vertebral joints start to loosen in older pets. The bones around the joint may remodel to try and re-stabilize the joint, which creates “bone spurs” known as spondylosis. Sometimes the meniscus between two unstable vertebrae may rupture, pushing material up into the spinal cord that causes pain or sudden paralysis. Left untreated, this “disc rupture” may be irreversible in as little as 24 hours. If a disc or other injury ruptures the spinal cord completely, a pet will be permanently paralyzed.
Signs Of Arthritis & Back Disorders
An arthritic joint may hurt when it is moved or even when it is at rest. A change in a pet’s behavior may be the first sign of arthritis. A common sign of pain shows when a pet that used to enjoy cuddling suddenly becomes standoffish. Likewise, a pet that used to keep its distance may start to seek out attention and comfort.
A pet may limp on one or more legs, be less playful, and spend a lot more time lying down or sleeping. It may be more irritable and act as if being petted is painful rather than pleasurable. It may eat less and drink less. Litter box accidents may be more frequent, because the pet doesn’t want to jump over the edge of the litter box. As the arthritis gets more severe, it may become incontinent, urinating and defecating on itself because it hurts too much to stand up and move to another place.
Rabbits, chinchillas, guinea pigs and hamsters with hip pain or back pain from arthritis often get dirty hind ends and may have feces and urine matted at the base of their tails and between their hind legs. This is because they have trouble curling around to clean themselves and eat their night stools (cecotrophs). You may find cecotrophs uneaten in their bedding. The skin may become red and irritated, a sign known as “scalding;” the skin may even start to ulcerate and slough.
Ferrets with back pain and arthritis may no longer do their “war dances.” They are more likely to grunt or cry when picked up and may even nip to express their discomfort.
Arthritic sugar gliders have trouble climbing and may use their hind legs together instead of independently. They rarely jump and glide anymore.
Rats, gerbils, and hamsters with back pain and arthritis often stop running on their exercise wheels, or spend much less time on them.
As mentioned earlier, certain back disorders may result in temporary or permanent paralysis. Which legs are affected depends on where the injury is located.
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