What is a joint?
A joint is a part of the body that connects two or more bones. Most joints in the body can move, which allows the bones to move in relationship to each other. Most movable joints are held together by an outer layer of tough, fibrous tissue called the joint capsule. The thin inner lining of the joint capsule, called the synovial membrane, produces joint fluid (synovial fluid) to lubricate the joint.
The ends of the bones are covered by a smooth layer of cartilage, called articular cartilage. The joint fluid and the articular cartilage reduce friction within the joint, allowing it to move smoothly. The articular cartilage does not contain any blood vessels to supply it with nourishment or oxygen. Instead, it receives some nutrients from small vessels in the bone underneath it and the rest by absorbing nutrients from the joint fluid.
What is degenerative joint disease (DJD)?
As cats age, the tissues that line their joints deteriorate and degenerate. Degenerative joint disease (DJD), also known as arthritis or, more specifically, osteoarthritis, is the result of gradual, irreversible deterioration of articular cartilage in one or more joints. Arthritis is a general description of any condition that causes inflammation in the joints.
The smooth and resilient cartilage degenerates and becomes brittle over time. With severe DJD, degenerated cartilage may break away from the bone and become loose within the joint. DJD can occur following several joint diseases, including infection, and may develop after bone or joint injury or surgery. Obese cats are more likely to develop DJD because of the chronic, low-grade inflammation caused by obesity and as a direct result of the mechanical stress that excessive weight puts on the joints.
Chronic, mild inflammation is involved in causing clinical signs. When the cartilage cells become damaged, they release substances that result in inflammation, causing pain and further damage to the cartilage. Once DJD begins, it can become a vicious cycle. As degeneration continues, the joint becomes more unstable. Scar tissue and/or bony growths form in the joint to stabilize it, further contributing to DJD.
What are the signs of DJD?
Most cats with DJD show only subtle symptoms, so DJD is often overlooked. The most common signs of DJD in cats include:
- Reluctance or inability to jump up or down from the furniture
- Not wanting to move (often perceived as “sleeping more”)
- Increased irritability when touched or handled (especially around the affected joints)
- Stiffness
- Reluctance to sharpen the claws
- Not wanting to groom
- Difficulty getting into or out of the litter box
Not every sign is observed in every cat with DJD.
Is DJD common in cats?
DJD is an under-recognized disease in cats. Recent studies suggest that it is a very common condition in cats of all ages, although the likelihood of a cat developing DJD increases with age. Studies found that 22% of cats older than 1 year and 90% of cats 12 years of age and older had evidence of DJD on X-rays. The most frequently affected joints are the hip, the knee, the tarsus (ankle of the hind leg), and the elbow.
How is DJD treated?
Most of the damage caused by DJD is irreversible. The goals of treatment are to improve the cat’s quality of life by minimizing pain and discomfort and to delay the progression of disease. You can improve the quality of life for a cat with DJD by providing pain relief and by changing the environment so they can get around more readily.
Some suggestions for modifying the environment include:
- Provide a step that allows the cat to get up to a favorite perching spot or sleeping area.
- Provide litter boxes with shallower sides.
- Place litter boxes on every floor of a multi-level home.
- Make sure that food and water dishes are easily accessible (you may need to raise them off the floor).
Encourage your cat to keep moving to maintain joint mobility and muscle tone. It may be helpful to have regular periods of gentle play using toys such as feathers or laser pointers (with rewards). Weight loss to achieve a healthy body condition is also extremely helpful at relieving arthritic pain.
What medications can provide pain control in arthritic cats?
Pain relief in cats can be problematic because they metabolize drugs differently than dogs. Cats are highly sensitive to side effects from acetylsalicylic acid (the active ingredient in Aspirin®) and acetaminophen (the active ingredient in Tylenol® among other over-the-counter medications). In fact, even a single acetaminophen tablet can be fatal to an adult cat. Always get your veterinarian’s advice before giving your cat any medication, and never give your cat any pain reliever meant for human use.
NSAIDs (nonsteroidal anti-inflammatory drugs) can be used to control inflammation in the joints and provide pain relief. Drugs used include meloxicam (brand name Metacam®) and robenacoxib (brand name Onsior®). A new, injectable anti-nerve growth factor (NGF) antibody treatment (Solensia®) can also be used to block one of the pain signals between the joint and the brain, helping your cat feel better.
Before giving your cat any pain medication, your veterinarian will recommend blood tests to ensure the liver and kidneys are functioning adequately and that there are no underlying conditions that could be worsened by these drugs. Your veterinarian will also recommend periodic monitoring of your cat’s liver and kidney function once they begin treatment for this condition.
Other medications that may be prescribed to treat pain caused by DJD include:
- Gabapentin — an effective drug for relieving pain, especially when given with other pain medications. It can often allow for decreased doses of other medications. It is used in human medicine to treat neuropathic pain and seizures. It can be used alone for early arthritic pain.
- Amantadine — a pain reliever that blocks the sensation of pain at the nerve pathways. It is not effective as a sole medication but increases the pain-relieving effect of other medications.
Your veterinarian may recommend injections of chondroprotectants (brand names Adequan® and Cartrophen®). These medications promote cartilage repair, help slow down cartilage damage, aid in other aspects of joint repair, and stimulate the production of more joint lubricating fluid.
Are diets or supplements helpful in controlling the pain of DJD?
Ongoing arthritis research has led to therapeutic diets that are formulated specifically to control the discomfort associated with DJD and to delay the progression of the disease. These therapeutic diets (including Royal Canin® Mobility Support and Hills® Prescription Diet j/d®) are available only through your veterinarian.
Nutraceuticals are nutritional supplements rather than pharmaceuticals (drugs):
- Omega-3 fatty acids are powerful antioxidants that help relieve inflammation in arthritic joints and are proven to decrease pain in cats with arthritis. They are a useful treatment in conjunction with other medications for any patient experiencing DJD or osteoarthritis.
- Undenatured type II collagen (Flexadin Advanced®) helps to modulate the inflammatory process in the joint and may reduce cartilage degradation.
- Green-lipped mussel (Antinol®) contains another fatty acid that has shown promising evidence to help cats with DJD.
- Two of the most used supplements are glucosamine and chondroitin. Some small research studies and numerous anecdotal case histories suggest these products are beneficial, and they appear to be free of side effects.
Some supplements are available over the counter (without a prescription). Since supplements are not highly regulated, some may not contain the labeled amount of ingredients and there may be quality differences between products made by different manufacturers. Your veterinarian may recommend a trusted brand.
What other treatments are available for treating DJD in cats?
Rehabilitation is a growing area of veterinary medicine similar to human physiotherapy. Certified rehabilitation practitioners offer many treatments for arthritis, including laser therapy, hydrotherapy, ultrasound, and muscle therapy. Acupuncture may also be an effective tool for pain relief.
Stem cell therapy and platelet rich plasma (PRP) injections are also used to treat arthritic patients in some veterinary clinics and referral hospitals. If you have any questions or concerns regarding the care and treatment of your cat, contact your veterinarian.