Health & Medical

Watch a small dog trotting along and then, mid-stride, skip a step — one back leg tucked up for a pace or two before dropping down and carrying on as though nothing happened. Owners describe it as a hop, a hitch, or a bunny hop. Most assume it is a quirk.

It is usually a kneecap sliding out of place.

The mechanics

The patella, or kneecap, normally sits in a groove at the bottom of the femur called the trochlear groove. The quadriceps tendon runs over it and attaches to the shin bone, and the whole assembly works like a pulley to straighten the leg.

The system depends on alignment. If the groove is too shallow, or if the bones are rotated so the tendon does not pull in a straight line, the patella pops out of the groove — luxates — usually toward the inside of the leg.

When it luxates, the dog physically cannot straighten that knee. So it holds the leg up. A few steps later, the muscle relaxes, the patella slips back into place, and the dog walks normally again. That is the whole explanation for the skipping gait.

Medial luxation, toward the inside, accounts for the large majority of cases and is the classic small-breed problem. Lateral luxation, toward the outside, is less common and more often seen in larger breeds.

Who gets it

It is overwhelmingly a small-dog condition, and it is largely genetic — a matter of skeletal conformation the dog was born with. Yorkshire Terriers, Pomeranians, Chihuahuas, Toy and Miniature Poodles, Cavalier King Charles Spaniels, Boston Terriers, French Bulldogs, and Jack Russells all appear on the high-risk list.

Cats get it too, less often, with Devon Rex and Abyssinians overrepresented.

Larger breeds are not immune, and in bigger dogs it more often accompanies other developmental problems like hip dysplasia or angular limb deformity.

Trauma can cause luxation in any dog, but if a small breed develops it gradually without injury, conformation is the reason.

Grading

Vets grade patellar luxation from one to four, and the grade drives the treatment conversation.

Grade 1: the patella can be pushed out of the groove by hand but returns immediately when released. It does not luxate on its own during normal activity. Many dogs with grade 1 never show a single sign.

Grade 2: the patella luxates occasionally on its own and returns either spontaneously or with manipulation. This is the classic skipping-gait dog, and it is the most commonly diagnosed grade.

Grade 3: the patella sits out of the groove most of the time and can be pushed back but immediately re-luxates. Gait is visibly abnormal, often with a crouched stance.

Grade 4: the patella is permanently out and cannot be replaced manually. The dog often walks with a very crouched posture or, in small dogs, sometimes moves on the front legs primarily.

Roughly half of affected dogs have it in both knees.

Diagnosis

A vet diagnoses this by hand. Feeling the knee while flexing and extending the joint and applying gentle pressure reveals whether the patella moves out of the groove and how easily. It takes seconds and requires no sedation for most dogs.

Radiographs come next if surgery is on the table, to assess bone alignment, look for arthritis, and check the hips. In larger dogs and in dogs with sudden severe lameness, the vet will also want to rule out a cruciate ligament tear, which frequently coexists — chronic patellar instability puts extra strain on the cruciate.

What to do about it

Not every case needs surgery, and this is where owners get conflicting advice.

Grade 1 and many grade 2 dogs are managed conservatively. That means keeping the dog lean, which is the single most effective intervention available, because every extra pound loads the joint. It means controlled exercise that builds the muscle around the knee — lead walks, gentle hill work, swimming — rather than the high-impact jumping off furniture that makes things worse.

Physiotherapy and hydrotherapy genuinely help. Joint supplements containing glucosamine, chondroitin, and omega-3 fatty acids are commonly recommended; the evidence is moderate rather than dramatic, but the omega-3 component has reasonable support for reducing joint inflammation. Anti-inflammatory medication is used for flare-ups under veterinary direction.

Practical home changes matter more than people expect. Ramps instead of jumping onto sofas and beds. Rugs on slippery floors, because a dog scrambling on laminate is stressing exactly the wrong structures. Nails kept short so the foot lands correctly.

Surgery is recommended for grades 3 and 4, for grade 2 dogs with persistent pain or worsening lameness, and for young dogs where progression is likely.

The surgery itself

Correction usually combines several techniques. Trochleoplasty deepens the groove so the patella has somewhere to sit. Tibial tuberosity transposition moves the attachment point on the shin so the tendon pulls in line. Soft tissue procedures tighten one side of the joint capsule and release the other.

Success rates are good — commonly quoted around 90 percent — with most dogs returning to normal function. Recovery takes eight to twelve weeks of strictly restricted activity, which is the part owners underestimate. Lead-only toilet breaks, no stairs, no jumping, no running. Rehabilitation exercises through that period improve outcomes noticeably.

Complications occur in a minority of cases and include re-luxation, implant issues, and infection.

Long-term view

Untreated moderate to severe luxation leads to cartilage wear and osteoarthritis over years, and increases the risk of cruciate rupture. Caught early and managed sensibly, many dogs live entire comfortable lives with a low-grade luxation nobody outside the family ever notices.

Because it is inherited, dogs with anything beyond grade 1 should not be bred. Buying from a breeder who has their breeding dogs' knees examined and graded reduces the odds considerably.