Page 363 - Canine Lameness

19.6 Stifle uxation 335

(A) (B) (C) (D)

Figure 19.16 Measurement of the femoral varus angle (FVA) is performed on (A) accurately positioned STIFLE REGION
craniocaudal radiographs of the entire femur. The (B) FVA is the angle formed between the (red line)
proximal and (black line) distal femoral axis. The distal femoral axis is a line perpendicular to the (blue
line) transcondylar axis, which is the line connecting the distal aspects of the lateral and medial femoral
condyles. Note that inaccurate positioning can result in false measurements as illustrated by images (C, D)
which are of the same patient that underwent surgical correction of MPL. Note that the femur appears
straight in image (C), while image (D) gives the (false) impression of femoral varus.

19.6.2 Physical Exam
The patient with stifle luxation will likely be non-weight-bearing with swelling and joint effusion
of the stifle. The source of lameness is generally obvious to identify. Palpation of the stifle typically
shows severe pain and therefore should be done after pain medications are administered.
Evaluation of the cruciate ligaments is performed by testing cranial and caudal drawer motion.
The collateral ligaments are tested by applying varus and valgus stress to the stifle (Video 3.1). For
testing the MCL, the examiner places one hand over the distal femur and one hand over the proxi-
mal tibia with the thumbs facing toward each other. Bracing the thumbs against the estimated
position of the MCL, the examiner applies valgus (i.e. levering distal limb laterally) stress to the
joint. If the joint opens up into valgus stress, the MCL has been compromised. The same is repeated
with the thumbs aligned over the lateral collateral ligament. If the joint opens up into varus insta-
bility, the lateral collateral ligament has been compromised.

19.6.3 Diagnostics
Standard, orthogonal stifle radiographs in addition to stress radiographs are helpful to further
define the extent of injuries and rule out any fractures. Radiographs will also show visible joint
effusion, soft tissue swelling, and joint subluxation or complete luxation (Figure 19.17), as well as
intra- or extra-articular avulsion fragments at ligamentous insertion sites.