Arthritis in cats (Proceedings)

Feline osteoarthritis (OA) is a growing problem in our veterinary patients.  We are discovering that it has been around and under diagnosed for years.  While we tend to think of cats as just a small dog, they are very different from their canine counterparts.  Cats come with a unique set or behaviors, personalities and diseases of their own. And OA in cats is very different from OA in dogs.

Knowing when a cat has OA is probably the hardest part of the disease.  Typically dog owners report lameness or a decline in exercise tolerance or endurance.  They have a specific leg they hold up or skip on.  Or perhaps they are sore in the morning but once they begin running they appear comfortable.  Owners are very savvy on OA in dogs and most have heard of hip dysplasia.  But cat owners and veterinarians are only now learning about what an arthritic cat looks like.  Cats can have a lamness or altered gait, but it is much less common than dogs to present for this complaint.  Cats may also exhibit stiffness when rising, which may be hard to discern from the normal cat nap stretch, which may be normal.  If a cat presents with overt or obvious pain or single leg lameness, the diagnosis may be easy.  But more commonly the signs will be much more subtle.

Personality changes are one of the most common observations in a cat with OA.  A normally affectionate cat may become nervous around new people or bustling activity around the house.  A happy playful cat may become depressed or withdrawn.  And a fun loving energetic cat may turn into an aggressive animal, biting family members or hissing at people when they are trying to pet or love on the family pet.  These personality changes may have previously been dismissed as a normal aging cat mood change.  But these character changes are not normal and should be addressed with the client to maintain a loving home environment and a good quality of life.  These may all be signs of OA and pain in cats.

Behavioral changes are also important indicators for feline OA and discomfort.  If the family cat changes from years of house training to disuse of the litter box, perhaps the box it too hard to climb into or located too far away to reach in comfort.  Litter boxes should be shallow and more numerable for cats with OA.  Normally you would want one extra litter box above the number of cats in a household, but with OA you will need more to be easily accessible without a long trek. If the cat normally climbs onto a sunny windowsill but has stopped sunbathing due to its height, this could be another sign of OA.  It may be too hard to jump up onto, or too painful when they jump down off of the high ledge.  The same can be seen for getting onto kitchen countertops or the family coach they used to love sharpening their claws on. 

Owners may think their pet has outgrown these less desirable habits, when in reality they may have stopped due to discomfort from these activities.  Stairs also pose concussive forces on painful arthritic joints.  Cats with OA are less likely to travel upstairs to family bedrooms where they used to sleep and snuggle.  If litter boxes are only located downstairs, cats are more apt to eliminate upstairs due to the effort required for an OA patient to travel to the normal laundry room or bathroom downstairs.  Another common behavioral change is a cat that would normally dominate the house has stopped chasing the younger cats or dogs.  If they normally torment housemates but have stopped doing so, the effort may be too much with arthritic joints and may not be an indication of a mellowing older feline, but a painful one.

Feline OA is much more prevalent than we previously thought.  One study of randomly selected cats showed 73% had evidence of OA.  Another study showed that elbow and hip joints are the most commonly affected in cats.  It also appears that most cats have at least four joints involved when they have OA.  There are several other studies looking at “asymptomatic” cats and the prevalence of OA.  The prevalence was 64% in older cats but still 16-22% of asymptomatic cats having radiographic signs of OA.  This body of knowledge supports that we are under diagnosing and under appreciating the discomfort in our elusive feline patients.       

Treatment of feline OA is similar to canine once the suspicion or diagnosis has been made.  Weight loss is a large component to minimizing the work the diseased joints are battling.  Keeping cats on the thin side of normal as well as a balanced nutritional plane is important.  Proper exercise should be encouraged for a good range of motion and joint comfort.  Their beds should warm and thick.  Beds should also be lowered from windowsills and be available on all floors in the house to minimize traversing stairs.  Massaging the cat and encouraging range of motion or stretching can be a bonding experience as well as helping to lubricate joints by circulating synovial fluid.  “Lazy” cats should be encouraged to walk by baiting with toys, treats or other positive reinforcement.  Commercial diets are now also available for cats and focus on weight loss with joint additives.

Nutraceuticals including chondroitin sulfate, glucosamine HCL, and omega acids are also available in feline friendly sizes and formulations.  Many come in feline friendly flavors or sprinkle formulas you can place on their food for ease in administration.  Pain medication are difficult in cats but there are options as well.  NSAIDs are available for short term use but not approved for long term management of OA in cats in the United States.  Tramadol and Gabapentin are used in cats with success.  Cats tend to be more excitable with tramadol and when this side effect is encountered, lowering the dose not help.  Also, splitting tramadol tablets to dose the smaller patients creates a very bitter taste, so it should not be added to food. 

OFA will certify cats and currently has 7 breeds with significant numbers including the Main Coon, which shows 18% affected.  PennHIP is currently only for dogs.  Surgical options are similar for cats and include Total Hip Arthroplasty (THA) and Femoral head and neck ostectomy (FHO).  THA is available in sizes for small dogs and cats.  Unilateral replacement is adequate for 80% of dogs.  The procedure is technically challenging and expensive.  There are cemented and cementless systems with templates and modular designs for a custom fit. 

The prognosis for a pain-free function is 95% having a good to excellent outcome.  Potential complications include infection, luxation, fracture, sciatic neuropraxia or implant loosening.  FHO is used to preserve limb function in severe OA when medical management is ineffective or when a THA has unrepairable complications.  It is typically performed in small dogs and cats but can be used when THA is not feasible.  It is less expensive and easier to perform than a THA.  The prognosis is good in smaller patients but much better is muscle atrophy is not severe.  Postoperative physical therapy is important to achieve a flexible pseudoarthrosis. 

Cats may also have OA in their stifle due to cranial cruciate ligament rupture.  The degree of lameness and age are used to guide whether surgical correction should be performed.  If the cat is non-weight bearing despite medical management, surgery should be considered.  If the cat is young and over 15 pounds surgery may be the better option for a quicker return to function and to minimize the progression of OA.  Cruciate repair techniques available in the cat include the extracapsular repair, cranial closing wedge and tibial plateau leveling osteotomy.  Medial patellar luxation may also be present in cats with stifle OA.  The Devon Rex and Abyssinian are particular prone to this condition.  It is also usually bilateral.  If the cat has a grade II or more, recurrent or continued lameness or also has a cruciate rupture, surgery should be considered.