Health test of Jack Russell Terrier - Pyrenean Mastiff | Jack Russell terrier | Gaspalleira Kennel

Patellar dislocation is one of the most common diseases of the canine knee, especially in dwarf and small breeds.

The patella (a bone embedded within the largest tendon of the hind limb, the quadriceps tendon) is normally held in place by two vertical bony walls (the trochlear ridges of the femur), which allow up-and-down movement (the movement that occurs when the animal flexes and extends its knee), but not movement of the patella over these trochlear ridges. When, congenitally (present at birth) or traumatically, the patella over the medial (inner) or lateral (outer) ridge, a medial or lateral patellar luxation occurs, respectively.

If the patella "dislocates," the animal experiences varying degrees of lameness, from small, intermittent hops on the affected limb to true non-weight-bearing lameness. This occurs because the patella pulls the entire quadriceps tendon with it—the tendon that controls half of the muscles surrounding the knee.

Along with this problem of improper quadriceps function, there are other associated problems, especially in the case of congenital hip dysplasia (HPD). Specifically, these animals often have deformities in the hip, femur, tibia, and tarsus (ankle). Because the severity of these deformities varies from patient to patient, not all HPDs are the same, and they are divided into four groups: Hip Dysplasia Grades I, II, III, and IV.

Grade I patellar luxation, for example, is characterized by infrequent patellar dislocation, and when it occurs, simply pushing it back into place is enough to hold it until the next dislocation. Bone deformities are practically nonexistent, and limping is either absent or minimal.

Grade IV patellar luxation, on the other hand, is characterized by a permanently dislocated patella, making it nearly impossible to manually return it to its original position. Deformities of the hip, femur, and tibia are severe, and the limp is typically non-weight-bearing and continuous.

First, the owner can already suspect the presence of a patellofemoral pain syndrome (PFPS) based on the way the dog limps and the breed and age of their dog:

They often begin by hopping on one leg, especially when going up steps or curbs, although they soon return to bearing weight on the knee normally. If the affected knee is manipulated, crepitus or cracking sounds of the patella can be detected as it moves in and out of the trochlear groove. It is also common in small breeds (especially Poodles, Yorkshire Terriers, Maltese, Pomeranians, etc.), which begin to have problems before their first year of life. Large breeds (especially Mastiffs, Great Danes, Newfoundlands, etc.) also have a special type of PFPS, the lateral type. Even so, PFPS can appear in ANY BREED AND AGE, so if it is suspected, the orthopedic surgeon must perform a complete examination of the knee.

The diagnosis of a limb-splitting injury (LSI) should be confirmed with basic manipulation, and then the accompanying deformities in the other bones of the limb should be quantified with an X-ray.

This step is especially important, as the surgical solution will depend on these deformities, as we will see later.

It is also important to rule out a concurrent (simultaneous) anterior cruciate ligament (ACL) rupture, since in many cases of LSI, this ligament is subjected to repeated stress until it results in a complete or partial tear.

Patellar luxation does not resolve spontaneously or with bandages or anti-inflammatories; it requires surgery. If the lameness symptoms are mild and occasional, the animal is often not operated on but is kept in a restricted activity mode with periodic checkups to prevent the mild luxation (Grade I) from progressing to Grades II, III, or IV.

In Grades II and III luxation, surgery is recommended even if the lameness is not very pronounced, since the patella, as it luxates and reduces (moves in and out), can eventually ulcerate and wear down due to friction against the trochlear groove of the femur (it's important to realize that this bone-on-bone rubbing motion can be repeated hundreds of times a day). Once these ulcers appear, the lameness will worsen and, in many cases, will be irreversible.

In the most advanced Grade (IV), the extreme deformity of the femur and tibia sometimes makes surgery impossible or inadvisable due to its poor prognosis. The surgical techniques that the traumatologist can use to resolve LR are very varied, and must be evaluated individually for each case, so the surgeon's experience is very important.

If diagnosed and treated early, the prognosis for reluxation of the kneecap is very good. Except in very extreme cases, the animal stops limping, and patellar reluxation and bone deformities can be controlled, provided the correct techniques are used. In the long term, the knee may develop osteoarthritis, but it is almost always mild and perfectly manageable, even without medication.