patella

THE PATELLA AND WHAT IT DOES:

The canine patella is equivalent to the human knee cap. It is a bony structure that sits in a groove in the femur (thigh bone) on the front of the stifle
(Knee Joint) Attached to the patella is the Quadriceps tendon and the patellar tendon. The quadriceps tendon runs from the patella up to the muscle
mass on the front of the thigh and to a lesser extent down over the patella tendon . The patella tendon runs from the patella down to a protuberance on
the front of the tibia. When the muscles contract, they pull the quadriceps tendon up which pulls the patella up, which, in turn pulls on the tibia via the
patella tendon. The result of all this pulling is to straighten or extend the leg. As the leg is extended and flexed, the patella rides up and down in the
trochlear groove. Ideally, the groove should be deep enough for the patella to fit snugly into it. If the tendons, muscles and bones are all aligned
properly, the result is a stable, sound stifle joint. Improper alignment means instability and this not only leads to degenerative joint disease, but also
places increased stress on other ligaments and supporting structures.

.Grade 1:
The stifle joint is almost normal and the patella luxates only when the leg is extended and the patella is pushed.
When the leg is extended, there is less tension on the tendons holding the patella in place, and it is therefore
easier to push out of place. Usually, there is no gait abnormality, but as the animal becomes older, it may
develop arthritis.

Grade 2:
The patella usually lies loosely in its normal position, but it will luxate medially with flexion of the joint. These animals have a "hopping" gait. The patella
becomes trapped out of the trochlear groove on flexion and the dog hops along on the other leg while kicking the sore leg straight to allow the patella to
move back into position. Animals with Grade 2 luxation are more likely to develop arthritis that thosewith Grade 1 because of the greater degree of
abnormal patella movement.

Grade 3:
The patella is dislocated most of the time, but can be put back manually of the leg is extended.

Grade 4:
The patella is dislocated all of the time and cannot be corrected without surgical intervention. Grades 3 and 4 show varying degrees of lameness, often
the dog assumes a crouched position due to the inability to fully extend the stifles; often they appear bowlegged with the toes pointed inwards due to the
deformities in the rear limbs.

The Luxating patella can be corrected.

The methods used for surgical repairs depend on how far the process has gone before intervention.
Surgical repairs may include any or all of the following:
1) The point of attachment of the patellar ligament is cut from the tibia and transplanted to its proper location to correct the in correct alignment.
2) The groove in the femur is deepened so the patella will stay in place.
3) The capsule around the joint is tightened. The last step is important because the joint capsule will have stretched during the period of luxation.
If surgery is performed before arthritis occurs, the prognosis is excellent. The dog will regain full use of its legs However if arthritis has already occured ,
the joint will still be somewhat painful, especially in cold weather.

Breeding with dog with luxating patella.

Because of the strong genetic relationships, animals with this disorder should not be used for breeding. They can still be excellent pets and those that
do require surgery will usually lead perfectly normal lives without any restrictions on activity.