Horses and dogs have a patella (knee-cap), like humans. The knee-cap is hanging loose in the knee and can therefore easily be moved.
On the picture below, you can see where the patella is located (see hind leg of the horse).
A horse at rest can block his knee-cap by means of clicking the knee-cap behind the condyle of the thighbone (femur). You can see this on the picture below, look at the left hind leg of the horse.
When the horse wants to move, the patella will be unlocked by contraction of the quadriceps muscle (is attached to the patella). In some horses, the patella stays blocked for a very brief moment. It looks like the horse knuckles down (his knee), and walks than again normal.
In some cases, the patella does not go easily back to his place. This is called patella fixation. The horse can no longer bend his knee (or stifle), and so the leg is dragged alone (see picture below). This can happen at one side or even at both sides. It occurs mostly in pony’s and young untrained horses.
This syndrome ameliorates by training, especially uphill, because this increases the growth of the muscles stretching the knee (stifle), like the quadriceps muscle.
In classical medicine, in some severe cases, the inner knee-ligament will be cut through.
In the dog, it is rather a patella luxation that will occur. This a shifted knee-cap (see picture below).
A luxation towards the inner side appears mostly in small breed, like the Chihuahua. A luxation towards the outer site of the knee (most appearing after trauma), is mostly seen in bigger breed, often in combination with a rotation of the thighbone.
When the knee-cap slips out only now and then, we speak about an intermittent patella luxation. These dogs walk occasionally some steps with one raised leg. Only at that moment, the knee-cap is shifted. After some steps, he falls back into place and the dog can walk again normally. This is frequently seen with the Jack Russel Terrier.
When the patella is continuously out of the groove, we speak about a continuous patella luxation. These dogs have difficulties in getting up and walking. They will walk with O-legs (kind of frog step). The worst form is when the patella can’t be put back at his place.
In animals where the knee-cap is replaced very often, intervention is necessary. For classical medicine, there is only 1 way to do so and that is surgery.
The quadriceps muscle plays an important part in this issue, in the horse as well as in the dog. This muscle receives his nervous impulses from the third lumbar vertebra. Osteopathic examination will show that the vertebras in this region will be blocked (show less mobility). As a consequence, the quadriceps muscle can’t function properly. After manipulation of this lumbar region, the nervous impulses will be normalized and the quadriceps muscle will be able to function normally. Therefore osteopathy can be very useful for this condition, as treatment and as preventive action.