Page 369 - Canine Lameness

19.10 ­ctrF tesrresres ooractoe ctrf ctofr ret o 341

deformity is difficult on physical exam, although some patients may show a compensatory gait of
stifle flexion to keep the tibial joint surface parallel with the ground.
ALD due to trauma, nutritional deficiencies, hypertrophic osteodystrophy, retained cartilagi-
nous cores, and other genetic/congenital skeletal dysplasias can result in various complex deformi-
ties. These deformities may result in secondary patellar luxation or hip pathology. Pure, isolated
frontal plane deformity of the proximal tibia is rare, but spontaneous proximal tibial valgus deform-
ity has been described in large- or giant-breed dogs (Olsen et al. 2016).

19.10.2 Gastrocnemius Injury
Injury to the origin of the Gastrocnemius muscle is a rare injury in dogs that may be caused by
acute trauma or chronic overuse. Gastrocnemius myotendinopathy has been described in both pet
or athletic, medium- to large-breed dogs and presents most commonly as none to mild, chronic
pelvic limb lameness (Kaiser et al. 2016). The lateral head of the muscle is typically affected.
Physical exam findings include pain upon palpation of the muscle origin at the medial supracon-
dylar tuberosity, stifle pain, and effusion, but with no stifle instability. Since the gastrocnemius
muscle is a stifle flexor and tarsal extensor, simultaneous stifle extension and tarsal flexion while
palpating the origin of the muscle may exacerbate pain. Radiographs may reveal chronic changes
(enthesopathy and mineralization) at the origin of the muscle and fabella (Figure 19.14) and mild
joint effusion. However, advanced imaging (MRI or ultrasound) is necessary to establish the diag-
nosis if radiographs are normal. STIFLE REGION
Acute, traumatic, and atraumatic avulsion of the muscle has also been reported. Likely this con-
dition describes the precursor of the above-described chronic myotendinopathy. However, clinical
symptoms can be more severe and result in non-weight-bearing lameness and a slightly dropped
hock, or even mild plantigrade stance. Radiographs may show distal displacement of one
(Figure 19.20) or both fabellae, fracture or fragmentation of the fabellae.

19.10.3 Long Digital Extensor Tendon Injury
LDE tendon injuries include rupture, luxation, and chronic tendinopathies. The LDE tendon can
be traumatically injured in dogs of any age, although avulsion fractures of the origin of the tendon
typically happen in juvenile animals (Fitch et al. 1997). Dogs with traumatic luxation, tears, or
avulsion fracture will have stifle joint effusion, pain with flexion of the stifle, and crepitus if the
injury is chronic. Iatrogenic laceration during the lateral approach to the stifle joint can also occur.
Luxation is a rare cause of lameness in dogs and can either be nontraumatic or traumatic. This
condition should be considered a differential diagnosis for “popping” sounds originating from the
stifle. The diagnosis can be made by placing a finger over the tubercle of Gerdy (located on the
lateral, proximal tibia) while placing the stifle joint through ROM. Clinical signs vary but may
include intermittent lameness or skipping gait making it a differential diagnosis for patellar luxa-
tion. Luxation of the LDE has also been reported as a complication after TPLO (Haaland and
Sjöström 2007). Calcification of the LDE tendon (Figure 19.20) has been reported in a dog that also
suffered from CCLD (Kennedy et al. 2014).
Radiographs may be normal or show cranial displacement of the fat pad with joint effusion. In
dogs with an avulsion fracture, a bony fragment may be seen in the craniolateral aspect of the
joint. The LDE itself can be imaged via MRI, CT, ultrasound, and arthroscopy. On ultrasound, the
LDE can be seen as a hypoechogenic linear structure just cranial to the lateral meniscus (Soler
et al. 2007).