What Is a Luxating Patella in Dogs?
A luxating patella — commonly called a “slipping kneecap” — is a condition in which the patella (kneecap) intermittently or permanently slips out of its normal position in the trochlear groove of the femur (thigh bone). Instead of gliding smoothly within the groove as the leg bends and straightens, the patella pops out of place.
The patella most commonly luxates medially (toward the inside of the leg) — this is the typical direction in small and toy breeds due to skeletal conformation. Less commonly, it luxates laterally (toward the outside), which is more often seen in large breeds.
Patellar luxation is one of the most common orthopedic conditions in dogs, affecting an estimated 7% of puppies — and up to 75% of toy breeds in some studies. It can be present at birth or develop over time. It is hereditary in many breeds, and breeding dogs with moderate to severe patellar luxation is strongly discouraged.
Which Breeds Are Most Affected?
Small and toy breeds are disproportionately affected by medial patellar luxation. Breeds with the highest predisposition include:
- Chihuahua
- Yorkshire Terrier
- Pomeranian
- Poodle (Toy and Miniature)
- Maltese
- Boston Terrier
- Pekingese
- Shih Tzu
- French Bulldog
- Bichon Frisé
Large breeds can develop lateral patellar luxation — Labrador Retrievers, Saint Bernards, and Akitas are among those sometimes affected. Large-breed lateral luxation often involves secondary complications such as cruciate ligament damage.
Grades of Patellar Luxation
Veterinary orthopedists grade patellar luxation on a scale of I–IV based on severity:
- Grade I: The patella can be manually luxated (pushed out) during examination but returns to normal position spontaneously. The dog shows no clinical signs.
- Grade II: The patella luxates spontaneously with normal activity and may stay out temporarily before returning. The dog may occasionally skip a step or hold up a leg briefly.
- Grade III: The patella is luxated most of the time but can be manually repositioned — though it immediately pops out again. Lameness is more consistent; the dog may have an abnormal gait.
- Grade IV: The patella is permanently luxated and cannot be repositioned manually. The dog walks in a crouching posture with legs rotated; surgical correction is essentially always needed.
Symptoms of Luxating Patella in Dogs
The most characteristic sign of patellar luxation is intermittent “skipping” — the dog suddenly holds up a hind leg for a few steps, then puts it down and walks normally as the patella slips back into place. This skipping may be subtle enough that owners attribute it to “just how they walk.”
Other signs vary by grade and progression:
- Occasional yelping or crying when the patella pops out
- Reluctance to jump, climb stairs, or exercise as before
- Bunny-hopping gait (using both hind legs simultaneously)
- Bow-legged or knock-kneed appearance in the hind legs
- Muscle atrophy of the affected limb over time
- Stiffness after rest
Cruciate ligament tears are a significant complication — repeated luxation stresses the cruciate ligament, and dogs with patellar luxation have a substantially elevated risk of developing a torn cruciate ligament over time.
Treatment: Surgery vs. Conservative Management
Treatment decisions depend heavily on the grade, the dog’s age and size, and clinical signs:
- Grade I: Usually managed conservatively. Weight management, joint supplements (glucosamine, fish oil), controlled exercise, and regular monitoring. Surgery is rarely needed.
- Grade II: Conservative management is tried first in many cases. Surgery recommended if the dog is symptomatic, younger, or the luxation is worsening.
- Grade III–IV: Surgical correction is almost always recommended to prevent progressive joint damage, pain, and cruciate ligament tearing.
Surgical techniques for patellar luxation may include:
- Trochlear modification — deepening the trochlear groove to better hold the patella
- Tibial tuberosity transposition (TTO) — repositioning the attachment of the patellar ligament for better alignment
- Soft tissue procedures — tightening the joint capsule on the side opposite the luxation
Most dogs require a combination of techniques. Success rates (returning to normal function) are generally 85–95% for well-performed surgery. Surgical cost in the US ranges from approximately $1,500–$3,500 per leg. Bilateral cases (both hind legs) require either simultaneous or staged surgeries.
Post-surgical rehabilitation (controlled rest, physical therapy, hydrotherapy) significantly improves outcomes and speeds recovery.