Each hind leg of a horse carries about 20% of its body weight. The horse's hind limbs are equivalent to its engines, which is reflected in the horse's stout hind limb bones, which are able to absorb and withstand great force in the process of pushing the body forward and upward.
First watch the video to review the explanation of the hind limb bones before ~ ~
The horse's hind limbs are closely connected to the spine by the sacroiliac joint (SIJ), which consists of the iliac wing and the transverse process of the first nominated vertebra.
The iliac joint, reinforced by dorsal and ventral ligaments, is barely mobile, but plays a very important role in propelling the body forward. Therefore, the iliac bone and the bone need to be firmly linked in order to transmit the thrust generated by the contraction of the muscles of the hind limbs along the spine to the forelimbs. The movement of this part of the spine that we see is actually derived from the lumbar-sacral junction (LSJ).
The complexity of the iliac area can be a source of back pain, but thick muscles make the problem difficult to diagnose. Whether attributed to the lumbar or iliac joints, the outward manifestations of pain include stiffness, behavioral changes, lack of motivation in the hind limbs, changing legs behind in canters while running, decreased quality of movement, reluctance to work from behind, reluctance to lift the back, and failure to change legs in the air perform flying changes) or refuse to jump.
Bones and joints of the hind limbs
The pelvis consists of three pieces of healing bone:
1. The iliac bone (illium) is the largest of them, located above the outer. Its highest point, the tuber sacrale, is where jumper's bump appears, while the tuber coxae on both sides forms the false hip joint. The prominence of the hip nodule is so obvious that it can be easily touched, so much so that people often confuse the hip nodule with the true hip joint at the back.
2. The ischium is located in the posterior lower part, which constitutes the posterior part of the pelvic floor, and there is a ischial nodule posteriorly, which is the point of buttocks that we use to measure body length.
3. The pubic bone (pubis) is located anteriorly and lower, constituting the anterior part of the pelvic floor. The pubic bone provides a broad adhesion surface for the abdominal and pelvic floor muscles, which is very important for tilting the pelvis and lifting the back.
The iliac, sciatic, and pubic bone combine in the middle of the outer side to form a deep cup-shaped joint fossa called acetabulum, which forms the hip joint with the lower femur. Although the hip joint belongs to the ball and socket joint and can do abductive movements, the attachment of ligaments and the position of the joints in the body limit the rotation of the hip joint.
The femur is the longest and heaviest bone in a horse's body. The femur is tilted forward and downward, with the tibia and patella forming the knee joint (stifle), which is equivalent to the human knee part.
The flying joint (hock) is a compound joint consisting of 3 rows of tarsal bones, distal fibula, and proximal metatarsal, equivalent to a human ankle. The anatomy of the flying joints, along with other hind limb joints, enables the horse to accelerate, slow down, spin sharply, and lift.
The fetlock, sesamoid, long pastern, short pastern, and pedal bone under the metatarsal bone have the same configuration as the forelimbs.
Conformation
The alignment, length and angle of the bones determine the bone configuration, balance and structural correctness. These are important indicators of a horse's athletic ability and long-term health.
Resources
Higgins G. 2012. Horse Anatomy for Performance: A Practical Guide to Training, Riding and Horse Care. David&Charles
CHEN Yaoxing. Anatomy of livestock and poultry. 3rd Ed. China Agricultural University Press
Britannica. Ball-and-socket joint
Equestrian Coach Blog. 2018. Stop Your Horse From Swapping Leads Behind in The Canter.
Wikipedia-Horse gait
5MinuteHorseLessons. 2011. Horse Gaits: What is Cross Firing or What is Disunited Canter? **see note below**
Equinews. 2011.Concussion in Movement of the Horse.
OPTIONS FOR ANIMALS.‘ Hunter’s Bump’
Hoofpicklife. 2021.Pelvic fractures in horses: all you need to know