Page 129 - Anatomy and Physiology of Farm Animals, 8th Edition

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(A) (B)
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Middle patellar Medial collateral
ligament
Lateral ligament
patellar
ligament

Medial meniscus (C)

Medial patellar Caudal
ligament cruciate
ligament
Lateral
collateral
ligament Cranial
cruciate
ligament

Figure 6-12. Equine stifle. (A) Cranial view of right stifle. Note the medial patellar ligament’s relationship
to the medial ridge of the femoral trochlea and the presence of the medial and lateral menisci within the
femorotibial articulation. (B) Medial view of right stifle. In this position the patella is locked over the troch-
lea and no muscular effort is required to keep the joint extended. (C) A sagittal section of the stifle showing
the cruciate ligaments, whose intra‐articular location provides cranial‐to‐caudal stability to the joint.

group (see Chapter 7) is a powerful
extensor of the stifle, acting through its
connection to the cranial aspect of the
proximal tibia via one (pig) or three (horses
and ruminants) strong patellar ligaments.
In the horse, the medial patellar ligament
is attached to the medial aspect of the
patellar via a large, hook‐shaped fibro-
cartilage. The combined cartilage and
tendon create a stout loop that can be
locked over the medial ridge of the femo-
ral trochlea at will (Fig. 6‐12, see also
Fig. 8‐15). In this position, the stifle is held
in extension with minimal muscular effort; Figure 6-13. Lateral radiograph of equine stifle
this anatomic arrangement therefore con- joint. Source: radiographs courtesy of Susan Kraft,
tributes to the ability of the horse to stand DVM.
while sleeping.
Occasionally, the patella of young sudden, inappropriate extension of the
horses may intermittently become locked stifle joint. This is called upward fixa-
over the medial ridge of the femoral tion of the patella; it is usually remedied
trochlea during gait and produce a with appropriate strength conditioning,