Page 358 - Canine Lameness

330 19 Stifle Region

for MPL or LPL, respectively). The decision on whether or not to pursue surgery is made on a case-
by-case basis taking into consideration the age, breed, and clinical symptoms of the patient, the
severity of luxation, as well as owner expectations. In general, lower-grade luxations in small-
breed dogs are often treated nonsurgically, while large-breed dogs more frequently require surgical
corrections including corrective osteotomies.

19.5.1 Signalment and History
Since patellar luxation is a developmental disease, the majority of dogs are diagnosed by
3 years of age. Neutered dogs are predisposed and by far the majority of patellar luxations are
diagnosed in small-breed dogs (O’Neill et al. 2016). While previously thought that MPL is seen
predominantly in small-breeds and LPL in large-breeds, this has been shown to be incor -
rect – medial luxation is by far the most common type of luxation, in both small- and large-
breed dogs (Bosio et al. 2017). However, LPL is by far more common in large-breed dogs (Kalff
et al. 2014; Di Dona et al. 2018) and rarely seen in small-breed dogs. MPL is commonly seen in
toy and small-breed dogs such as Pomeranian and Yorkshire Terrier (O’Neill et al. 2016).
Large-breed dogs commonly affected include Labrador and Golden Retrievers, Pit Bulls,
Huskies, and Bull Dogs.
STIFLE REGION ranging from nonclinical, to the typical symptoms of “skipping” pelvic limb lameness, to severe
Dogs affected with patellar luxation may present with varying degrees of clinical symptoms

skeletal deformities and abnormal posture (Video 19.5). The symptoms depend on the severity of
the deformities and degree of patellar luxation. Dogs with high-grade (Box 19.2) luxations are
more likely to have angular limb deformities (ALDs), severe gait abnormalities, and postural dis-
abilities. These severe abnormalities generally become apparent early in puppyhood. Dogs with
Grade 2 luxations will show an intermittent non-weight-bearing lameness when the patella luxates
and therefore are more likely to be presented to the veterinarian then dogs with Grade 3 luxations.
The latter show a more consistent lameness that, particularly if bilaterally present, may not be
recognized as an abnormality by owners. Dogs with Grade 1 luxations will generally not show any
clinical signs. Similarly, they may present as puppies (when deformities are severe) or the diagno-
sis may be an incidental finding during routine examination.

Video 19.5

Patellar luxation gait.

Traumatic patellar luxation is poorly described in the veterinary literature. This condition is
generally described as traumatic rupture of the retinaculum without any skeletal deformities.
Onset of lameness is acute and moderate-severe pain is associated with the inciting cause.

19.5.2 Physical Exam

Patellar luxation is generally diagnosed based on physical exam findings and the degree of deform-
ity is evaluated radiographically. The disease may affect both limbs, requiring careful examination
of both stifles. However, most often one side is more severely affected clinically.