Page 368 - Canine Lameness

340 19 Stifle Region

19.9.1 Nontraumatic Patellar (Ligament) Desmopathy
Patellar ligament thickening and desmopathy has been described following tibial tuberosity
advancement (TTA) and TPLO in up to 80% of the cases (Dan et al. 2019). This is thought to occur
due to increased stress placed on the ligament. In most cases, it does not result in clinical lameness
and appears to be self-limiting.
A similar condition may be observed in patients that have not undergone surgical treatment. As
with people (Dan et al. 2019), it may be caused by chronic overuse and intense athletic activities.
The authors have observed it in large-breed, athletic dogs. Lameness is typically progressive and
intermittent, with worsening of pain during exercise and jumping.
Physical exam may reveal varying but typically mild degrees of pelvic limb lameness. Tenderness
or pain may be elicited with direct palpation of the ligament and flexion of the stifle. Some cases
have visually evident or palpable patellar ligament thickening.
Thickening of the patellar ligament (or surrounding region) is easily recognized radiographically
but it may be difficult to differentiate patellar ligament from abnormal peritendinous soft tissues.
To assess the structural integrity of the ligament, ultrasound or MRI can be used. Using a combina-
tion of physical exam findings of a thickened, painful patellar ligament, plus soft tissue specific
imaging allows the best assessments for therapeutic intervention.
STIFLE REGION 19.9.2 Patellar Ligament Laceration/Rupture

Traumatic patellar ligament desmopathy is an uncommon injury in dogs (Das et al. 2014) and is
associated with high leaps and falls, bites, lacerations, and other traumas. Any breed of dog is sus-
ceptible to sharp trauma. However, puppies are more likely to avulse the tibial apophysis rather
than rupture the tendon from falls and other trauma. Iatrogenic laceration has been described as a
complication of stifle surgery (Das et al. 2014).
On physical exam, rupture of the patellar ligament prevents active stifle extension and causes
involuntary stifle collapse during the stance phase. If sharp trauma is suspected, the stifle should
be examined for lacerations or wounds. A chronically ruptured tendon may be thickened. In cases
of complete tears, the patella will be displaced proximally throughout flexion and extension ROM.
The stifle may be painful especially if other tissue trauma is present.
A lateral radiograph in the flexed and extended position can document a proximally displaced
patella, particularly in stifle flexion, as well as thickened tendon and any avulsion fragments when
present. With complete rupture, the patella is located proximal to the trochlear groove due to the
contraction of the quadriceps. Imaging of the tendon itself with ultrasound or MRI allows visuali-
zation of integrity of the remaining tendinous soft tissue.

19.10 Other Diseases Affecting the Stifle Region

19.10.1 Angular Limb Deformity

The most common types of stifle joint ALD are an excessive TPA (i.e. a TPA of 35° or greater) and
frontal and transverse plane deformities of the femur. The latter is a common cause of patellar
luxation in dogs. The former generally presents in combination with (and because of symptoms
associated with) CCLD and has been reported to be associated with early neutering in large-breed
dogs (Duerr et al. 2007). It can also be the result of undetected or untreated proximal tibial physeal
injury/fracture. As sagittal plane deformity is generally well tolerated in dogs, observation of this