FINDON VET  08 8347 3444   221 Grange Road, Findon SA 5023

SEATON VET  08 8155 5200   342 Tapleys Hill Road, Seaton SA 5023

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Medial Luxation of the Patella

Medial patella luxation repair surgery is offered at the Findon Vet Surgery and has excellent results. 

At Findon and Seaton Vets we are serious about obtaining the very best outcome for pets undergoing medial patella luxation surgery. Our procedures are advanced, and give the best surgical results, with rapid return to function (use of the leg that had surgery). However, this is not enough. Rehabilitation is always recommended and takes the form of passive exercise and massage, introduction of controlled exercise in a controlled environment, and management of weight bearing.


Cat Medial Patella Luxation:

For more information on Cat knee injuries, which usually involve MORE ligaments being torn than in dogs, please

Click On: Cat ACL and Knee Dislocations.


Pets having CRUCIATE, PATELLA or ORTHOPAEDIC surgeries at either Findon Vet or Seaton Vet receive THREE MONTHS FREE use of our Accell therapy.


Medial patella luxation is the dislocation of the patella (knee cap) to the middle side of the knee (or stifle).

This can be the result of trauma or injury to the stifle that occasionally also involves a fracture of the patella, ie a broken knee cap, or more commonly as a result of congenital anatomical factors, ie bent leg bones.

A medially luxating patella causes significant secondary damage to the stifle, the knee, resulting in arthritis. In many individuals, this arthritis becomes severe and debilitating. All dogs that dislocate their knee cap should have protective treatment given, antiinflammatories at the time of the injury, and Zydax injection treatments, given preferably as a course of four injections, every 6 months.

Medial patella luxations are graded with grade 1 being when the knee cap slips easily in and out of its groove on its own, there is no pain and the only sign may be the occasional skip on the back leg. Surgery is not advised but Zydax injection course is highly advised to minimise arthritis.

For more information on the different Grades of Medial Patella Luxation and treatment advice for each, CLICK HERE >>

All other Grades of medial patella luxations (grades 2, 3 and 4) are advised to have surgery.

1.     Medial patella luxation as a result of congenital factors:

Many small breeds of dogs have leg bones that are quite bent and when x-rayed from the front we can see a significant "S" bend from the outward aspect of the femur which then bows inward just above the knee or stifle, and then the tibia bows outward from just below the joint of the stifle and then bends back and straightens as it gets towards the ankle or hock. See the x-ray to the right ... note the patella sitting right over to the right, which is the medial side, well dislocated from the groove it should be sitting in!

The end result affects the direction of the pullling forces of the muscles and tendons of the stifle, with the greatest force being the massive quadriceps muscle of the thigh that attaches to the front of the tibia, via its tendon (the patella tendon) in which is the actual patella or knee cap.

Because of the bend inwards through the knee region, the attachement of the quadriceps/patella tendon is now to the middle side of the knee. It should be straight down below the knee. Every time the quad muscle contracts, which is every time the dog is walking or running and pulls the lower leg forward, and every time the dog is standing and supporting its weight, the pull on the patella is to the middle side of the groove of the front of the knee.

Eventually this will stretch the ligaments that hold the kneecap in its groove and will allow the kneecap to finally ride up on top of the medial trochlea ridge, the middle side ridge of the kneecap groove. When this happens and the dog bends its knee at the same time, it is like placing a lever under the kneecap and this tears the remaining ligament that was trying to hold the kneecap in its groove From this point onwards, the knee cap will constantly dislocate.

2.      Medial patella luxation as a result of injury or trauma.

Occasionally dogs with excellent conformation of their hind legs, ie they are straight boned, will suffer medial luxation of their patella. This is always due to an accident of some kind, there may have been a blow to the knee for the side, or the dog may have been turning and thus twisting the knee and then pushed off running and the patella ligaments on the outside, lateral side , have torn. Sometimes the knee cap actually fractures.

Dogs that suffer a medial patella luxation due to an accident are in severe acute pain and will hold their leg up from the time of injury. They may eventually place a little weight on this leg but surgery is required.

Have a look at the x-ray at left. There is certainly a little bowing and this would play a factor in the dislocation. Once the knee cap has luxated medially (the knee to the left side), note that the tibia (the bone below the knee) becomes more twisted, accentuating the bow. You can clearly see the patella on the left hand side of the picture sitting to the medial side of the knee or

stifle, whereas on the right hand side you can see the patella sitting perfectly in its groove.

Medial patella luxation and anterior cruciate ligament rupture.

When the anterior cruciate ligament is ruptured, the lower leg, tibia, is free to move forward when weight is placed on the leg. This is painful, however, so initially the injured leg will be lifted off the ground. The force of the original injury that ruptured the

anterior cruciate ligament sometimes also tears the ligaments to the side of the knee cap that hold the knee cap in its proper position in its groove.

Because the tibia is unstable and moves forward if any weight is placed on it, the patella tendon that attaches to the top front of the tibia, causes the patella to lift out of its groove, and the loss of the lateral ligaments of the patella mean that it will luxate, dislocate to the medial side.

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221 Grange Road, Findon SA 5023

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