Surgery gets bark of approval to fix dog’s knee
KNEE problems in dogs are seen commonly by vets, and the most frequent reason for this is cranial cruciate ligament (CCL) disease. The knee of the dog is stabilised, not specifically by the shape of the joint, as in ball and socket joints (hip) and hinge joints (elbow), but relies more on ligaments, joint capsule and cartilages.
Essentially, the knee joint has two rounded ends to the femur that are coated with cartilage that rest on a relatively flattened tibial table. The tibial table has two “C” shaped cartilages called menisci that are designed to accept the rounded femur ends (trochlea).
The major ligaments of the knee internally are the cruciate ligaments, so called because the two ligaments cross over each other, the one ligament preventing forward slip of the femur and the other the opposite slip.
The knee is further stabilised on the sides by the collateral ligaments, and finally by the capsule. The ligament that is most often the problem is the cranial cruciate ligament, known in humans as the anterior cruciate ligament (ACL).
In animals the ligament may gradually deteriorate and then suddenly rupture, whereas in humans the rupture is normally associated with a specific severe injury.
If the ligament ruptures suddenly, there is a discernible loss of use of the leg; initially it will be held in the air, the knee may be swollen and painful but after a few days you will see your dog using the leg a little again, albeit with a limp.
If you look carefully you may see some of the other tell-tale signs: “toe touching” or placing of the foot on the tips of the toes with minimal weight bearing. A slight twist of the lower leg with the ankle rotated outwards, and the “sit sign” where the affected leg is held straight out when sitting.
Diagnosis is based on a physical examination by a vet. Manipulation of the knee should reveal a diagnostic looseness in the joint which indicates ligament damage. This may have to be done under sedation as it can be painful. X-rays are helpful in aiding the diagnosis and important in planning the therapy.
What to do about it?
This is a physical problem that most often requires surgery to provide an acceptable recovery. The surgeries that are effective are myriad and should be based on the patient’s specifics – size, weight, activity level and age.
Small patients normally do well with a repair that involves the use of a ligament “mimic” placed in a similar alignment to the damaged ligament, lying just outside the joint capsule. The tissues in that area gradually deposit scar tissue along the line of the prosthetic ligament that ultimately take over the function of the damaged ligament.
Large (12kg plus) and highly active dogs benefit more from surgeries that obviate the need for an intact CCL.
It may seem strange that to repair a ligament we actually cut and move bone but it works really well, has been extensively researched, and gives long-term results. The accepted results achieved by most surgeons are in the region of 90% of dogs doing well after surgery.
Some variances do come into play with damage to the cartilage and existing bony changes (osteoarthritis) resulting in a more negative outcome. In all of the cases, physiotherapy helps speed up and result in optimal recovery.
As with any problem there is generally more than one way to solve it.
Many other procedures have been tried and some are still used in practice, with varying results. Older procedures include using thick fibrous strips from the thigh muscle placed through drilled tunnels in the knee to anatomically mimic the CCL, to newer patented methods using very strong fibres placed through drill holes.
Some vets even inject blood into the joint in the hope that the ligament will heal and
that sufficient internal irritation from the blood will cause scarring and stabilisation of the knee. This
has been repeatedly refuted in literature but offers a cheap alternative to surgery.
Stem cell therapy can be used as an adjunct to surgery to aid in healing and cartilage regeneration, as can the use of platelet rich plasma.
All in all, surgery seems to be the best option, with very good longterm results and a happy, comfortable pet in most cases.