Patellar Luxation: At a Glance
Common in Chihuahuas, Pomeranians, Yorkies — early detection prevents arthritis.
Grade
| Grade | Description | Symptoms | Treatment |
|---|---|---|---|
| Grade 1 | Kneecap manually luxates, returns spontaneously | Occasional skip, no pain | Weight management, joint supplements |
| Grade 2 | Kneecap luxates spontaneously, returns manually | Frequent skip gait, mild discomfort | Surgery recommended if symptomatic |
| Grade 3 | Kneecap permanently luxated, manually reducible | Constant lameness, moderate pain | Surgery strongly recommended |
| Grade 4 | Kneecap permanently luxated, irreducible | Severe lameness, bone deformity | Surgery essential, complex procedure |
Surgery Success Rate by Grade
Patellar Luxation Warning Signs
| Sudden 'skip gait' — hopping on one back leg for a few steps | |
| Intermittent lameness that resolves on its own | |
| Reluctance to jump or climb stairs | |
| Visible 'popping' sensation when manipulating the knee | |
| Leg held up while walking, then suddenly 'normal' | |
| Progressive bow-legged stance in severe cases | |
| Normal gait with no skipping or hopping | |
| Bilateral hind leg weakness in senior dogs only |
Grade 1-2 luxations can often be managed conservatively with weight control, joint supplements (glucosamine/chondroitin), and avoiding high-impact activities. Surgery is reserved for dogs with frequent symptoms or Grade 3-4 luxations.
Untreated patellar luxation leads to abnormal wear on the knee joint, causing early-onset arthritis. Dogs with Grade 3-4 luxations may develop permanent bone deformities if not corrected before skeletal maturity (12-18 months).
Patellar luxation is a kneecap that slips out of its normal groove at the front of the knee, graded 1 to 4 by severity and how easily it can be manually put back in place. It's most common in small and toy breeds, Yorkshire terriers, Pomeranians, Chihuahuas, and Boston terriers among them, and most often slips toward the inside of the leg. A dog that occasionally skips on a rear leg for a few steps and then walks normally usually has a milder, lower-grade case, while a leg that's constantly held up or can't bear weight at all needs a vet exam right away.
Patellar luxation
A kneecap that slips out of its groove, most often in small and toy breeds
petstore.comWhat a skipping rear leg means
Small and toy breeds carry most of the risk
Yorkshire terriers, Pomeranians, Chihuahuas, and Boston terriers are among the breeds most often affected, and the kneecap most commonly slips toward the inside of the leg (medial luxation) rather than the outside.
The four grades of severity
A dog can run, play fetch, and jump onto the couch for years with a kneecap that isn't actually staying where it belongs. The classic "skip-hop" most owners notice, and often dismiss as a one-off stumble, is frequently the very first visible sign.
This condition matters because it's not rare: it's one of the more common orthopedic issues in small and toy breeds specifically, and left unaddressed at higher grades, it changes how a dog's whole leg develops and moves. Catching it at a mild grade gives you far more options than catching it after years of an untreated, worsening gait.
A Kneecap That Doesn't Stay in Its Track
The patella, or kneecap, is supposed to glide up and down a groove at the front of the knee joint as the leg bends and straightens. In patellar luxation, the kneecap slips out of that groove, most commonly toward the inside of the leg (medial luxation) rather than the outside, and small and toy breeds are disproportionately affected, likely tied to how their leg bones and the groove itself are shaped.
The classic sign is a dog that skips or hops on one rear leg for a few strides, then suddenly plants the foot and walks normally again, as the kneecap slips out and then pops back into place on its own.
Grades 1 Through 4 Describe How Far It's Progressed
Veterinary grading runs from mild to severe. In Grade 1, the kneecap can be manually pushed out of place but returns to the groove on its own, and signs are mild or infrequent. Grade 2 means the kneecap slips out during normal movement or manipulation and stays out until the knee straightens or it's manually repositioned. Grade 3 means the kneecap is out of place most of the time and can be pushed back manually but slips out again as soon as pressure is released. Grade 4 is the most severe: the kneecap is permanently displaced and cannot be manually corrected at all, and affected dogs often walk with a crouched, bent-knee gait.
Higher grades are generally more visible and constant, which is also why they tend to get caught later than a subtle Grade 1.
Treatment Follows the Grade, Not a Blanket Rule
Mild, low-grade cases are often managed conservatively, with weight control and joint support, since surgery carries its own risks and recovery time. Moderate to severe cases, where the kneecap is out of place often or permanently, typically need surgical correction to prevent long-term joint damage and lasting changes to how the leg bears weight.
The dog that skips for two steps today and seems fine tomorrow isn't necessarily fine; it's giving you the earliest version of a sign that gets much harder to fix the longer it's left to progress on its own.
The Merck Veterinary Manual grades patellar luxation from 1 to 4: Grade 1 is mild and infrequent with the patella spontaneously returning to the groove after manual displacement; Grade 2 luxates with stifle flexion or manipulation and stays luxated until extension or manual replacement; Grade 3 is luxated continually, reducible manually but reluxates spontaneously; and Grade 4 is permanently luxated and cannot be manually reduced, with severe lameness and limb deformation. The manual notes that conservative management is reserved for mild cases while moderate to severe cases generally require surgery.