e matter of establishing a diagnosis is difficult in
many instances and in some cases impossible.

The femeropelvic articulation is formed by the hemispherical head of the
femur and the acetabulum; the latter constituting a cotyloid cavity
which is deepened by the cotyloid ligament.

The round ligament (ligamentum teres) is the principal binding structure
of the hip joint and it arises in a notch in the head of the femur and
is attached in the subpubic groove close to the acetabular notch.
Another ligament, peculiar to Equidae--the accessory (pubiofemoral)--is
attached to the head of the femur near the round ligament and passes
through the cotyloid notch and along the under side of the pubis. It
is inserted or blends with the prepubic tendon. This ligament prevents
extreme abduction of the leg. The joint capsule encompasses the
articulation and is attached to the brim of the acetabulum and the edge
of the head of the femur.

[Illustration: Fig. 40--Sagital section of right hock. The section
passes through the middle of the groove of the trochlea of the tibial
tarsal bone. 1 and 2. Proximal ends of cavity of hock joint. 3. Thick
part of joint capsule over which deep flexor tendon plays. 4. Fibular
tarsal bone (sustentaculum). A large vein crosses the upper part of the
joint capsule (in front of 1). (From Sisson's "Anatomy of the Domestic
Animals.")]

[Illustration: Fig. 41--Muscles of right leg; front view. The greater
part of the long extensor has been removed. 1, 2, 3. Stumps of patellar
ligaments. 4. Tuberosity of tibia. (From Sisson's "Anatomy of the
Domestic Animals.")]

The stifle joint is analagous to the knee joint of man and is to be
considered an atypical ginglymus (hinge) articulation formed by the
femur, tibia and patella. The ligaments are femerotibial, femeropatellar
and capsular.

In addition to the usual provision for articulation of bones there are
situated cartilaginous _menisci_ between the condyles of the femur and
the head of the tibia. These discs surround the tibial spine and are
otherwise shaped to fit perfectly between the articular portions of the
femur and tibia.

Collateral ligaments (internal and external lateral) pass from the
distal end of the femur to the proximal portion of the tibia. The mesial
(internal) arises from the internal condyle of the femur and is attached
to a rough area below the margin of the medial (internal) condyle of the
tibia. The lateral (external), shorter an