Patellar Luxation in Dogs: Breed Risk, Grades & Treatment (UK Guide)
on September 18, 2026

Patellar Luxation in Dogs: Breed Risk, Grades & Treatment (UK Guide)

Short answer: patellar luxation means the kneecap slips out of its normal groove, and it's far more common in small and toy breeds than most owners realise — UK vet records show it affects around 1 in 77 dogs, with Pomeranians, Chihuahuas, Yorkshire Terriers and French Bulldogs at five to six times the risk of a crossbred dog. Below is what's actually happening in the joint, the real breed and bodyweight risk data, the four-grade scale vets use, and when it genuinely needs surgery rather than management.

Written by Jamie Sinclair, who writes about canine health, nutrition, and everyday care for Doggy Dailies — focused on translating veterinary research and real ingredient science into practical, honest guidance UK dog owners can use.

Table of Contents

What Is Patellar Luxation?

The patella (kneecap) normally sits in a groove at the end of the femur called the trochlear groove, sliding smoothly up and down as the knee bends. Patellar luxation happens when the kneecap slips out of that groove, sideways — almost always towards the inside of the leg (medial luxation) in small and toy breeds, or towards the outside (lateral luxation) in larger breeds. It's a structural, largely developmental problem rather than an injury in most cases: shallow trochlear grooves, misaligned thigh bones, and loose supporting ligaments all make it easier for the kneecap to pop out of place, and once it does, the abnormal movement itself gradually worsens the misalignment over time.

The Real Breed & Bodyweight Risk Data

This is worth grounding in real numbers rather than the vague sense that "small dogs get wobbly knees." A VetCompass study analysing UK primary-care veterinary records found patellar luxation diagnosed in 1.30% of dogs in a single year — roughly 1 in 77 — making it a genuinely common orthopaedic condition, not a rare one (O'Neill et al., 2016, Canine Genetics and Epidemiology). Eleven breeds showed significantly elevated risk compared with crossbred dogs, with four standing out clearly: Pomeranian (6.5 times the risk), Chihuahua (5.9 times), Yorkshire Terrier (5.5 times), and French Bulldog (5.4 times). Toy breeds as a group carried 3.7 times the risk of non-Kennel-Club-recognised dogs.

Two findings genuinely surprise most owners. First, it was dogs below their breed's average bodyweight that carried the higher risk — 1.4 times the odds compared with dogs at or above the breed mean, and dogs under 10kg specifically had 2.4 times the odds of dogs weighing 10-19.9kg. This runs counter to the instinct that extra weight on the joints is always the driver; here, being a smaller, lighter-boned individual within an already small breed is the bigger factor. Second, neutered dogs had 2.4 times the odds of entire dogs, and females had 1.3 times the odds of males. Age matters too: the median age at first diagnosis was 4 years, and dogs 12 years or older were actually less likely to receive a first diagnosis than dogs under 3 — consistent with this being a largely developmental condition that tends to show up, if it's going to, relatively early in life.

The Four Grades of Patellar Luxation

Vets classify patellar luxation on a 1-4 grading scale that determines the right treatment path, based on how easily the kneecap moves and whether it stays in place:

  • Grade 1 — Clinical signs are mild or the dog may show none at all. The kneecap can be manually pushed out of place but returns to the groove on its own.
  • Grade 2 — The kneecap luxates on its own or with manipulation and can stay out of place temporarily, returning to the groove manually or when the leg is extended. Dogs often show intermittent, "skipping" lameness.
  • Grade 3 — The kneecap is out of place most of the time, can be pushed back manually, but slips out again easily. Lameness is consistent and visible bone deformity has usually developed by this stage.
  • Grade 4 — The kneecap is permanently out of place and can't be manually returned to the groove. Lameness and limb deformity are severe, and affected dogs often walk with a crouched, bent-legged gait.

(Merck Veterinary Manual)

Signs and Symptoms

  • An occasional "skip" or hop in the back leg, sometimes described as the leg giving way for a stride or two before returning to normal
  • Intermittent lameness that comes and goes, often worse after exercise or rest
  • Reluctance to jump or a change in jumping style
  • A bow-legged or "cow-hocked" stance in more advanced cases
  • Visible difficulty straightening the leg fully
  • In severe, longstanding cases: a permanently bent, crouched gait

How Vets Diagnose It

Diagnosis usually starts with a physical exam: your vet will manually manipulate the kneecap to see how easily it luxates, whether it returns to the groove on its own, and grade it accordingly. X-rays are often used to assess the degree of associated bone deformity (particularly relevant for grades 3-4) and to help plan surgery if it's needed. Because patellar luxation is frequently found incidentally during a routine check in dogs showing no obvious symptoms, especially at Grade 1, many cases are picked up before the owner has noticed anything at all.

Treatment: Conservative vs Surgical

Treatment depends heavily on the grade and how much it's actually affecting the dog:

  • Grade 1, and mild Grade 2 cases with no significant lameness — often managed conservatively: weight management, controlled exercise, physiotherapy, and joint-supportive care, with regular vet monitoring since luxation can worsen over time.
  • Grade 2 with consistent lameness, and Grades 3-4 — generally need surgery. Common techniques include deepening the trochlear groove so the kneecap sits more securely, repositioning the tibial tuberosity (the bony attachment point the kneecap's tendon pulls against) to correct alignment, and tightening or releasing soft tissue around the joint as needed.

In the UK VetCompass data, of the new cases identified in that year, 39% were managed with medication alone, 13.2% went to surgery, and a further 3.7% were referred on to a specialist — a useful reminder that most diagnosed cases, particularly the milder grades, are managed rather than operated on.

Supporting a Dog With Patellar Luxation

  • Keep your dog at a lean, appropriate weight for their frame — given the data above, this is about avoiding extra joint stress generally, not because being overweight is what causes the condition in the first place
  • Provide controlled, regular exercise rather than sporadic bursts of high-impact activity (repeated jumping on and off furniture is worth minimising in predisposed breeds)
  • Use ramps or steps for dogs who jump on and off sofas, beds, or into cars, particularly in toy breeds already carrying elevated risk
  • Keep nails trimmed and paw pads groomed, since poor traction on slippery floors can worsen an already unstable joint
  • For milder, conservatively managed grades, a joint-support supplement can be a sensible part of the everyday routine alongside your vet's plan — our Hip & Joint Mobility Chews combine glucosamine, chondroitin and green-lipped mussel to support general joint comfort, though they support the joint rather than correcting the underlying luxation itself
  • Follow your vet's specific rehabilitation plan closely after any surgery, since outcomes depend heavily on controlled recovery

When to See a Vet

  • Any skipping, hopping, or intermittent lameness in a back leg, even if it resolves quickly and your dog seems fine afterward
  • A change in jumping behaviour or reluctance to use stairs
  • A visibly bow-legged stance or crouched gait
  • Any of the higher-risk breeds above showing even mild, occasional signs, given how much more common this is in that group
  • A known Grade 1-2 diagnosis that seems to be progressing (more frequent skipping, more consistent lameness)

FAQ

What is patellar luxation in dogs?

It's when the kneecap slips out of the groove it normally sits in, usually towards the inside of the leg in small breeds. UK vet data shows it affects around 1.30% of dogs in a given year.

Which dog breeds are most at risk of patellar luxation?

Pomeranians, Chihuahuas, Yorkshire Terriers, and French Bulldogs carry five to six-and-a-half times the risk of a crossbred dog, and toy breeds as a group carry roughly three-and-a-half times the risk.

Does being overweight cause patellar luxation?

Not according to the UK data — dogs below their breed's average bodyweight actually showed higher risk than heavier dogs, suggesting the condition is more about individual bone and ligament structure than excess weight, though keeping a healthy weight still reduces general joint stress.

Does every dog with patellar luxation need surgery?

No. Milder grades, particularly Grade 1 and some Grade 2 cases, are often managed conservatively with weight control, exercise management, and monitoring. Surgery is generally reserved for Grade 2 cases with consistent lameness and Grades 3-4.

What does a dog with patellar luxation look like when walking?

Often an occasional skip or hop in a back leg that resolves within a stride or two. In more advanced, untreated cases, this can progress to a permanently bent, crouched gait.

Can patellar luxation get worse over time?

Yes. The abnormal movement of an unstable kneecap can gradually worsen the underlying joint misalignment, which is why even mild, intermittent cases are worth monitoring with your vet rather than ignoring.

Sources

This article is for general information only and isn't a substitute for veterinary advice. If your dog shows skipping, lameness, or a change in gait, please contact your vet for an examination and grading.

Related: More Joint & Mobility Guides