Luxating patella in dogs: why does my dog skip a few steps on three legs?

Your three-year-old Yorkie is racing round the park when suddenly he lifts a back leg and goes a few steps on three legs, like a child playing hopscotch. Then he puts the leg down and carries on as if nothing had happened. It happens two or three times a week. Or at his booster the vet mentioned in passing that he has "a slipping kneecap, grade two" and you never got round to asking what that meant. A luxating patella is one of the most common orthopaedic problems in small breeds, and very often this is exactly what it looks like.

When to call the vet today

The patella is the small bone at the front of the knee. Normally it glides in a groove at the bottom of the thigh bone. When it luxates, it slips out of that groove, usually towards the inside, and the leg locks for a few seconds or a few steps. That on its own is not an emergency. Call the same day if:

• he has not put the leg down at all for a few hours, or yelps when you touch it;
• the knee is swollen, warm or sitting at an odd angle;
• he is lame on both back legs, walking hunched or cannot get up;
• the lameness started after a jump or a slip and is not wearing off within a few steps (it may be a torn ligament, which is more common in knees with an unstable kneecap);
• a puppy's back legs are visibly bowed and he is finding it harder and harder to walk.

For a brief skip that comes and goes, book an appointment in the next few weeks. Do not leave it for years.

What to film and note at home

Filming

At the practice he is nervous and walks perfectly. At home, film him from behind and from the side, at a walk and a trot, for several tens of seconds, on a surface that is not slippery. If you catch a skipping episode on video, that is the best evidence you can bring.

The diary

• how many times a week he skips and how long it lasts;
• which leg (often both, one worse than the other);
• what he was doing at the time: running, turning sharply, getting off the sofa, climbing stairs;
• how he "fixes" the leg. Some dogs flick it out behind them, as if kicking, and the kneecap pops back in by itself;
• whether he is slow to get up in the morning or after a nap;
• what he weighs now.

What the grades mean

Your vet will probably give you a grade from 1 to 4. So you know what you are hearing:

The grade tells you how unstable the kneecap is. How much it bothers the dog also depends on his age, his weight, how well muscled his thighs are and how often the kneecap slips.

Which dogs get it

A kneecap that slips inwards is typical of small and toy breeds: Yorkshire Terrier, Chihuahua, Pomeranian, toy and miniature Poodle, Bichon, Maltese, Shih Tzu. Large dogs get it too, less often. It is usually inherited, comes down to the shape of the leg bones and often shows from puppyhood.

What the vet will check

1. History and the video. How long, how often, which leg, what the dog does when it happens.
2. Orthopaedic examination. The vet feels the knee with the dog standing and lying down, gently pushes the kneecap inwards and outwards, and sees how easily it leaves the groove and whether it goes back. That gives the grade. They also check the knee ligaments, because cruciate ligament rupture is more common in knees with an unstable kneecap.
3. The rest of the legs. Hips, the other knee, the spine. In small breeds, hip pain can look a lot like a knee problem.
4. X-rays, for the shape of the bones and for arthritis. They are done before any surgery anyway. In dogs with severe deformity, sometimes a CT scan too.
5. The plan. It depends on the grade and on how much it bothers the dog.
   • Low grades without frequent lameness: weight kept in check, regular exercise, well-built muscles, sometimes rehab exercises with a veterinary physiotherapist, and periodic check-ups.
   • High grades, or a dog who is often lame or in pain: your vet will talk to you about surgery, which deepens the groove and moves the point where the kneecap attaches. Ask what it involves, what the few weeks of recovery look like and what results it gets in dogs like yours.
   • For pain and inflammation, the vet chooses the treatment.
6. Check-ups. An unstable kneecap wears the knee over time and opens the door to arthritis. A yearly check with his weight recorded helps a lot.

Ask, too, whether the problem runs in your dog's line. A dog with a luxating patella should not be bred from.

What not to do at home

• Do not force the kneecap back in. If your vet has shown you how and the leg is stuck, do it gently. Otherwise let the dog pop it back himself.
• Do not give human painkillers. Many are toxic to dogs, even in small amounts.
• Do not let him jump off the sofa or the bed. Jumping down from height and landing on wooden floors is what knocks the kneecap out. A ramp or a soft step makes a big difference.
• Do not keep him on slippery floors. Put down rugs or non-slip runners, especially where he likes to run.
• Do not let him put on weight. One extra kilo on a four-kilo dog is a quarter of his body weight, carried on the same knees. For low grades, losing weight is sometimes the treatment that helps most.
• Do not stop exercise altogether. The thigh muscles hold the kneecap in its groove. Regular on-lead walks over varied ground, at his own pace, do him good. Sprints and sharp turns do the damage, especially chasing a ball thrown a long way.
• Do not swap the vet visit for joint supplements. They may help alongside treatment, but they will not put the kneecap back.
• Do not put off an orthopaedic check because "it wears off in a few steps". Every episode rubs away a little cartilage, and at ten the knee carries every episode that came before.

If it comes to surgery

Recovery usually takes a few weeks: rest in a small space, short on-lead walks that get gradually longer and, ideally, exercises with a veterinary physiotherapist. Your vet gives you the exact plan. The hardest part for you will be keeping him quiet during the weeks when he already feels fine and wants to run.