What it is
The kneecap is a small bone that glides up and down a groove at the lower end of the thigh bone each time the leg bends and straightens. If the groove is shallow, or the thigh bone, shin bone and surrounding muscles are not lined up quite straight, the kneecap can be pulled sideways and slip out of place. While it is out, the leg cannot straighten properly, which is why the dog skips or holds the leg up.
The condition can be present from birth, linked to the shape of the leg and to a small build, though larger dogs can have it too. An injury can also knock the kneecap out of place.
Each time the kneecap slides out and back, it rubs on the edges of the groove, so the joint wears over time. A lean, fit dog that moves steadily, rather than leaping and twisting sharply all day, puts less strain on its knees.
Signs you may notice
- Skips on three legs
- Holds a hind leg up briefly
- Kicks the leg out backwards
- Oddly bent knees
- Reluctant to jump
You may notice the dog suddenly skipping for a few steps on three legs with a hind leg held up, then running on as if nothing happened. Some dogs stretch the leg out backwards until the kneecap slips back, or walk with oddly bent knees.
When to see a vet
Book a visit if your dog skips on a hind leg now and then, and contact a vet soon if it starts limping all the time or will not put weight on the leg.
This is general information, not veterinary advice. For your own dog's health, tests and treatment, see a vet.