MPL in small dogs: why your dog skips a step on walks

If your small dog suddenly skips on a hind leg mid-walk — a hop or two, holding the leg up, then back to normal as if nothing happened — you are very likely watching a luxating patella. The kneecap (patella) is slipping out of its groove, usually toward the inside of the leg, then popping back in.

Medial patellar luxation (MPL) is the most common orthopaedic condition I diagnose in small breeds: Poodles, Pomeranians, Chihuahuas, Maltese, Yorkshire Terriers and French Bulldogs are all over-represented. It usually stems from shallow groove anatomy and limb alignment, so both knees are often affected.

We grade it 1 to 4. Grade 1 is a kneecap that can be pushed out but returns by itself; Grade 4 is permanently out with the leg unable to fully extend. The grade, plus how much it bothers the dog, drives the decision: many Grade 1 and mild Grade 2 dogs are managed conservatively, while Grade 3–4 and Grade 2 dogs with frequent lameness generally do best with surgery.

Why operate? A kneecap that repeatedly slips damages cartilage every time, and over years the result is arthritis and progressive bowing of the leg — in growing dogs it can deform the whole limb. Surgery (deepening the groove, realigning the attachment point) has high success rates, and recovery in small dogs is usually straightforward.

For dogs being watched rather than operated: keep them lean, build hind-limb muscle with controlled exercise, and avoid slippery flooring where possible — rugs make a genuine difference to a dog with unstable knees.

If the skipping is becoming more frequent, the leg is being held up longer, or your dog is becoming reluctant to jump or climb stairs, the grade may be progressing. That is the moment for a reassessment, not the moment to keep waiting.