Patellar Luxation in Cats: The "Dog" Knee Problem That Happens in Cats Too
Ask most people about a "luxating patella" and they'll picture a small dog, since it's one of the most commonly diagnosed orthopedic problems in toy breeds. Cats get it too. It's less talked about, partly because it's genuinely less common and partly because cats are so good at compensating for it that owners often don't notice until it's fairly advanced.
| Quick facts | |
|---|---|
| What it is | The kneecap slipping out of its normal groove |
| Underlying cause | Usually a developmental or genetic groove and alignment issue |
| Typical onset | Can be present from a young age, sometimes not noticed for years |
| Breed risk | Devon Rex, Abyssinian, Siamese and British Shorthair overrepresented |
| Typical treatment | Depends on severity, from monitoring to surgical correction |
What's actually happening in the knee
The patella, or kneecap, is supposed to glide up and down within a groove at the end of the thigh bone as the leg bends and straightens. When that groove is too shallow or the leg's alignment pulls the kneecap sideways, the patella slips out of place instead of staying in the track. VCA Animal Hospitals notes that in cats this almost always means the kneecap slips toward the inside of the leg (medial luxation), which is the same direction seen in most small dogs with the condition.
How common it actually is
A 2021 study of 107 pedigree cats in the Czech Republic, published in the journal Animals, found patellar luxation in close to a third of the cats examined, most of it mild. The same study noted that Devon Rex, Siamese, British Shorthair and Abyssinian cats have been identified in prior research as overrepresented for the condition, with the Devon Rex showing the strongest predisposition of all. Nearly 18% of the cats in the study had both patellar luxation and hip dysplasia at the same time, which points to a broader skeletal alignment issue rather than an isolated knee problem in some cats.
The four-grade scale vets actually use
Severity is classified on a standard four-grade scale, and it's worth understanding because grade drives almost every treatment decision that follows.
| Grade | What it means |
|---|---|
| Grade I | Kneecap can be pushed out of place by hand but returns on its own when released |
| Grade II | Kneecap pops out on its own sometimes and needs the leg extended to slide back in |
| Grade III | Kneecap is out of place most of the time but can still be pushed back manually |
| Grade IV | Kneecap is permanently out of place and can't be repositioned by hand |
Why it's easy to miss
Cats are light, flexible and very good at redistributing weight off an uncomfortable leg without ever developing an obvious limp. PetMD notes that mild cases are frequently found incidentally during a routine exam rather than because an owner noticed a problem. What owners do sometimes catch is a brief skip or hop mid-stride, a leg held up for a step or two, or a cat that seems less inclined to jump than they used to.
Treatment and outlook
Grade I luxations often don't need surgery at all and are simply monitored over time. The Cat Fanciers' Association notes that cats with grade I through III luxations generally do very well with surgical correction when it's needed, with a low chance of the problem coming back afterward. Grade IV is a tougher case: even after surgery, roughly half of these cats see the luxation recur, which is part of why catching and addressing this earlier, before it progresses to the most severe grade, leads to a meaningfully better long-term outcome.
Frequently asked questions
Does every cat with patellar luxation need surgery?
No. Mild, grade I cases are often just monitored, especially if the cat isn't showing pain or lameness. Surgery becomes the more common recommendation as severity increases.
Can patellar luxation affect both back legs?
Yes, and it often does, since the underlying alignment or groove depth issue is usually a developmental trait rather than a one-off injury to a single leg.
Is this the same problem dogs get?
It's the same basic mechanism and grading system, though it shows up less frequently in cats overall and tends to get diagnosed later since cats hide the resulting discomfort so well.
This article is for general information and isn't a substitute for advice from your own veterinarian, who can grade and manage joint problems in your specific cat.
