SURGERY
Grade Description
Grade 1 Patella can be luxated but spontaneous luxation seldom occurs. Once the patella has been luxated during clin-
ical exam, the patella spontaneously reduces when the examiner releases pressure. The patella is stable in the
trochlear in full range of motion
Grade 2 Angular and rotation deformities of the femur may be present. The patella can be luxated and
remains luxated through full range of motion unless reduced by the examiner. The animal can
clinically reduce the patella and this is seen with the skipping gait. Once reduced the patella
remains in the trochlear groove for the full range of stifle motion
Grade 3 Angular and rotational deformities are often present. The patella remains luxated most of the
time. The patella can be reduced by the examiner however normal range of motion of the stifle
lead to luxation of the patella
Grade 4 Moderate to severe angular limb deformities are often present. The patella is permanently
luxated and cannot be reduced to the trochlear groove at any point in the normal range of motion
of the stifle. The trochlear groove itself is often shallow or convex
Table 1. Grading Patella luxation in the dog
condyle. Other studies have shown an increased angle of
inclination of the femoral neck is associated with patella
luxation in small breed dogs. Large breed dogs seem to
have a relatively normal conformation of the femur when
compared with small breed dogs. However large breed
dogs with MPL tend to have a relative degree of patella
alta (high-riding patella - structurally found more proximal
in the trochlear groove) when compared to the confor-
mation of normal large breed dogs, this may be cause or
consequence of MPL in large breed dogs.
SURGICAL REPAIR
Surgical repair of patella luxation should be performed
on animals showing clinical signs of lameness associated
with the patella luxation or in young animals to prevent the
long-term complications later on in life from the patella
Figure 2A
luxation. The main goal of surgical repair is re-alignment
of the patella-quadriceps mechanism leading to normal
sliding of the patella in the patella groove. Surgical repair
has two categories, a release or an augmentation of the
soft tissue components and corrective distal femoral os-
teotomy (CDFO) or tibial crest transplant (TCT).
It has been shown that soft tissue procedures performed
without correction of the bone deformities have a high
failure rate and should never be used as a sole method
of repair. Surgical complications using the current tech-
niques are reported as high as 85-48%. Surgical compli-
cations using the TCT in combination with soft tissue re-
pair techniques are reported to be as high as 20%. These
complication rates should be considered to high for a
condition that is relatively common. (Fig 2a, 2b)
Figure 2B
Issue 03 | JUNE 2017 | 13