Every horse owner should strongly understand horse anatomy or the different horse body parts. We’ll look at the horse frame from the outside down to the skeletal structure and even a diagram of a horse. Understanding the horse’s characteristics can ensure that you keep your horse healthy and diagnose injuries to specific body parts.
Anatomy of the Equine Skeleton
The horse skeleton consists of 200 different bones in the head, body, and legs. On the inside, every horse has the same horse parts, from the bone structure to the ligaments and horse muscles. But the size and look of the outer system can vary by equine race and gender.
A horse’s head can weigh up to 16 kg (large horse). The proportions of the head to the body are one distinct factor that varies by the type and race of horses.
Horses with big heads have cold-bloodedness which gives them better pull strength due to building more ballast on the front of the body. In comparison, horses with small heads are typically saddle horses with better resilience for quick or long runs due to a lessened burden to the body’s front.
Horsehead anatomy says the head has two parts – neurocranium (the top) and viscerocranium – the muzzle (bottom). Then, in the top half, there is the occiput – where the head joins with the neck right behind the ears.
The forehead is also the front of the head below the ears. This area usually has a forelock growing out of the crown.
And the crown is the area in front of and between the ears that lines the eye fovea, the temples, the temporal fovea, the forehead, and the eyes and eye sockets.
The muzzle – the bottom part – has the nose, nostrils, and nostril wings, upper and lower lip, chin, cheeks covering the wide, flat jaw which sticks out underneath, branches of the jaw (the bottom edges), the chin groove, and the muzzle edges and groove.
There are four head shapes found in horses with differing features.
- Noble, straight profile
It is perfectly balanced with a straight line between the nose and forehead. Forms a broad forehead with a short bottom part and long top half of the head, typically seen in racing and breed horses.
- Dished – concave
Broad forehead, large nostrils and eyes, and a concave line between the nose and small falcate ears. This look is mostly seen in Arab horses, including half-Arabs.
- Roman nose
A convex line to the nose with a short neurocranium and a longer bottom half with long ears and small nostrils and eyes compared to the size of the head and the narrow forehead. Signature features of racehorses and cold-blooded breeds, including Kladrubers and Lipizzaners.
- Pig head
Disproportionately shortened muzzle with small nostrils
The shape of a horse’s ears depends on the steed. Warm-blooded horses have thinner, lighter ears with pointy tips vertically positioned on the head.
While cold-blooded horses have fleshier ears with rounded, blunt tips covered with thick hairy fur, diagonally positioned to the head.
But anomalies also exist for horse ears, including:
- Donkey ears – long, broad, and thick
- Pig ears – flops to the front
- Hare ears – narrow and long
- Mouse ears – round-tipped small, and short
- Lop ears – drops to the side
The behavior of the ears – mobility – can refer to a horse’s temper. If your horse’s ears twitch and move too much, it may be a sign of the horse’s nervousness or hyperactivity. But if there is no sign of movement, it could mean the horse is deaf.
Did you know that horses fall into the category of mammals with the biggest eyes? Their eyes are 1.5 times bigger than adult human eyes.
The equine eye has three membranes – the outer fibrous layer has the transparent cornea. And the middle vascular layer has the iris, while the inner membrane is the retina.
Their eyes are on both sides of the head, giving a visual line of most stuff at their sides and back. And they have a three-dimensional triangular view in the front of the muzzle.
However, horses also have a blind spot along the tail line, which can cause the horse to react instinctively with a kick if they sense something behind them that they can’t see.
Teeth and a Horse’s Age
By examining a horse’s teeth, you can see the equine’s age accurately. In particular, pay attention to the incisors and the sockets on the cutting surface. The deeper the sockets, the older the horse.
As horses age, they also start to experience teeth that push towards the front and lean. You can notice these changes along the jaw intersection.
An equine neck is also the lever. You can tell a lot about your horse’s condition, the quality of training, and disposition to sports by the neck’s length, proportions, and muscles.
The neck controls the horse’s balance. The neck has three parts – the right and left side, the throat, and the forelock and back of the neck. Therefore, there are three types of neck classifications:
- Straight (ideal) – straight trachea that allows for more air intake in shorter amounts of time for a correct shape
- Swan – when the neck creates an arch with the bottom and upper edges (often seen in Arab horses)
- Close-coupled – the bottom is convex with a concave upper part for a high head carry that results in frequent tripping. Also, difficulty with breathing because the convex shape of the base can block the trachea’s airflow (less preferred and most flawed type)
It’s less rare to see a swan or close-coupled neck shapes. While straight necks are typical, the degree can also vary between a high, low, or properly set neck.
The term barrel refers to the torso and the body’s back parts that protect the organs. Various parts make up the barrel.
The highest point on the barrel is the withers, the area where the neck meets the torso. There are crucial muscles in the withers, requiring that they be properly shaped, high, visible, and broadly stretched towards the back.
Withers that are flat, indefinite, or pointy can be due to faulty training, flawed anatomy, adiposis, or malnutrition. It also refers to how you measure a horse, from the ground to the highest point on the body, defined in hands.
The chest also matters in that it needs to be the appropriate size to hold the lungs and the heart. A long, broad, and deep chest is preferred, as too wide will be slower due to being heavier.
But narrow chests have less room for the lungs and heart to function, making it more difficult for the horse to support a rider.
The correct chest shape would be arched ribs and an average broad breast. But a wider chest can indicate a swaying gait, while a more narrow breast isn’t safe for a riding horse.
A horse’s flank is a sensitive area that covers the kidneys. This filled, less concave flank is on both sides between the croup and the trunk.
When bathing your horse, avoid this area during cold weather. And when cleaning the site, use a delicate touch.
The back connects the front of the horse with the rear half via the spine. Therefore, your horse needs a properly muscled and shaped back to support and transfer a rider’s weight from the front to the back limbs.
The cervical spine starts at the neck behind the head and connects to the dorsal vertebrae, which connect the ribs. This section attaches to the lumbar vertebra, which then connects to the sacral vertebrae behind the rear legs. And it extends down the tail bone via the caudal vertebrae.
Other than the correct back shape, there can also be the convex or roached-back. A convex occurs when the back grows short and arches upward, with a strong, hard, and stiff shape that can create an uncomfortable, rough walk.
A long-backed horse has an improper muscle structure. And a concave or swayback shape can weaken the spine due to a low cohesiveness in the vertebrae.
This issue can be a birth defect or an acquired development seen in mares bred multiple times, old steeds, and cold-blooded species.
A horse’s limbs refer to the legs, joints, tendons, and hooves at the highest risk of injury. Many injuries occur due to preventable causes like improper care or negligence.
The muscles, leg length, proportions, strength, and flexibility are limb factors that change based on the horse’s race.
Cold-blooded horses have weak yet thick limbs with joints that have clear edges. Oval edges can signal a lymph problem. But horses with hot blood have compact, dry stems.
The purpose of the front legs is to keep the body upright, and it can buffer the shocks that occur during movements. Most of the horse’s weight also sits on the front legs.
Because the front legs are closer than the back legs to the center of gravity, they experience more injury from being ballasted. In addition, both forelimbs extend from the scapula – shoulder blade – down to the hoof bone – navicular.
In the middle, there are the:
- Humerus (arm bone)
- Radium (forearm bone)
- Ulna bone
- Elbow joint
- Carpus (knee joint and bone)
- Cannon (large metacarpal)
- Split (small metacarpal)
- Fetlock joint
- Pastern joint
- Coffin joint
The stifle joint is the most complex, equivalent to a human knee. It contains the femur (thigh bone), patella (kneecap), and the tibia (shin) with two joints – the femoropatellar joint (connects with the kneecap) and the femorotibial joint (connects with the bones).
The hip joint has limited movement due to being a femoral head surrounded by large muscle mass and intra-articular ligaments.
And the fetlock joint attaches to the sesamoid bones, the proximal phalanx, and the cannon bone. The front legs also have the knee – the carpus or carpal joint, made with two rows of little carpal bones that attach the radius (top of the knee) with the splits and cannon (bottom).
The coffin joint is the wedge bone found in the hoof, made of three individual bones – the middle phalanx (pastern bone), distal sesamoid (navicular bone), and distal phalanx (coffin bone).
There are several types of front limb builds, in addition to the correct position:
- Base narrow – the limbs get closer at the bottom instead of being parallel, resulting in stickling – when the front legs step on the back ones)
- Base wide – from the knees down, the legs bow outward, which results in gait stiffness
- Toes out – The limb has an inward arch while the fetlock-hoof axes turn the outside.
- Pigeon-toed – when the fetlock-hoof axes lean towards the inside, causing a walk with outward arches
- Knock-kneed – Legs resemble a large X due to the limb axes breaking in the knee joints and bowing towards the inside. The walk can become strickle or inward arches.
- Bowlegged – when the front limbs have a barrel wall shape that causes extra strains on the inner limbs and outer tendons.
The shoulder blades connect to the front limbs and determine the horse’s physical abilities. Your horse should have freedom of movement with the blades diagonally positioned, wide, and long.
The powerful hind legs have several functions – add power to the gaits, carry the coup, and improve strength and dynamics during jumps.
The back limbs have some of the same bones as the front legs, plus the hock and gaskin. These limbs start at the pelvis and connect to the navicular bone in the hooves. The back horse leg anatomy includes the bones:
- The femur (thigh)
- Stifle joint
- Hock (Tarsal) joint and bone
- Large and small metacarpal
- Fetlock and pastern joint
- Coffin joint
The carpus or carpal knee – referred to as the knee – is on the front legs, but in the back legs, it’s the tarsus, referred to as the hock, and connects the tibia and tarsals. Nine bones and several ligaments combine to make the three main joints of the hock – intercarpal, radiocarpal, and carpometacarpal.
Hocks that grow too narrow or too short can get damaged more often and faster. Other issues that can occur with the hock include:
- Bursitis is when an egg-shaped swelling occurs along the top of the heel’s bulb. If there is a protrusion of the skin, it’s acquired bursitis. It becomes true bursitis if the heel bursa becomes inflamed but doesn’t cause lameness (referred to as a beauty defect)
- Spavin (bone spavin) – the most incurable and serious issue – growth from the bone causes the joint to deform and small bones to knit, ending the horse’s ability to move. It starts as an inflammation that becomes lameness, which doesn’t disappear after curing the lameness in intense activities.
- Bog spavin – acquired or congenital disability of a convexed protrusion caused by the position of the heel bone, inflammation of the fascia – the piece that keeps the tendons around the hock – or a fascia overgrowth over the hock.
- Popped splint – splint bone growth of the capitulum. It doesn’t usually cause lameness but can spread to nearby tendons and cause irritation or tenderness on narrow, short joints.
- Windgalls – soft swelling around the hock and fetlock joints caused by exudative and synovia fluid filling a growing joint pouch. It could be swelling caused by a diet with too much protein or excessive training. Articular windgalls occur as they press against the common and move to the other side. Worse type.
The posture of the back limbs, when viewed from the side, can be correct or:
- Camped-under – when the legs go too far under the belly.
- Camped-out -when the rear legs are too far forward to the chest and stress the joints and tendons (not the same thing as laminitis)
- Knee sprung – a birth defect that causes the knee joint to break towards the front at the axis. It may be asymptomatic or symbolized by balance problems, stumbling, or gait struggles.
- Calf-knee – carpus grew to the back.
From the back, horses’ back legs can be:
- narrow (when limbs grow too close together)
- stands wise – (when there’s bow-leggedness in the front but flared outward on the back – rare and seen more in starved horses)
- stands close (narrow base of the front legs)
- bow-legged (legs turn inward while hocks turn far from each other and back legs shape into a barrel’s walls, seen as the legs making arches and going inward in movement with hoof depends with each step)
- Cow-hocked (axes break in the hocks towards the inside and an advanced posture fault, resulting in overloading the ligaments and tendons in the back limbs.
You also need to know about the horse leg’s cannon bone. When there are cannon bone faults, it can cause the limbs to weaken.
Potential faults of a horse pastern include:
- Too much straightening of the pastern
- Calf-kneed – pastern, straight, short)
- Thin hocked
- Coon-foot (pastern’s outer edges are unparalleled and closer together at the carpus’s top
- Tied-in – too thin and narrow
- Disproportionately long pastern to the cannon bone’s length
Healthy hooves are a crucial component of a horse’s overall health. Every step of the hooves causes the blood at the bottom of the legs to move back up and towards the heart. A characteristic rotting smell and sensitivity are two noticeable signs of hoof rot.
The anatomy of the hoof – a horse’s foot – consists of the hard outer wall, epidermal laminae, stratum medium, white line, and the inner sole. At the back of the hoof, there is the angle of the sole, the heel bulb, the frog, and the central sulcus.
Other issues that can occur with the hooves include:
- Improper size – too big or small
- A narrow hoof that causes a disappearing frog
- Steep – when the front of the hoof has a steep angle but with vertical side walls – a birth defect or an ailment or sign of the tendons contracting
- Valgus hoof – acquired or congenital disability that causes the flexor tendons to shorten – most weight goes on the front of the hoof while the back wall never touches the ground.
- Post-laminitis – deformed walls with transverse rings due to acute inflammation
- Blunt edges – due to front legs having a camped-under or camped-out back leg posture
- Diagonal – one wall is concave or perpendicular due to faulty posture.
- Flat – causes hoof damage from the rocky or hard ground.
- Sharp edges – camped-out or camped-under postures in back or front legs due to bad shoeing or cleaning
- Crooked – one wall is convex, and the other is concave due to uneven weight distribution – usually caused by a faulty limb posture.
Tail and Croup
Evaluate the croup by width, length, angulation, and muscles. A croup without the proper proportions can affect the use of a saddle.
There are three croups types when viewed from the side:
- Normal – 15 to 25-degree pelvic slope toward the ground
- Flat (straight, horizontal) – less than a 15-degree pelvic slope
- Sloping (truncated) – 30 to 40-degree slope
Flat croups are most often seen in noble horses like the Arabs. This shape allows the horse to have a faster, elongated gait. But it can lose movement strength, reducing the ability to jump, have quick starts, or carry weight.
A sloping croup adds strength, which is better for carriage. It’s also good for jumping due to its great takeoff strength. But it won’t allow for fast speeds.
From the back, there are three coups:
- Normal – rounded, oval, wide, well muscular shape
- Sloping – The quarter lines form a roof with the sacrum (end of the spine) being the top. Can be a beauty defect when properly muscled
- Wide – hips are nearly the same level as the sacrum with a noticeable indent – most common in cold-blooded types
The tail can be normally positioned high, as in Arabs, or cold-blooded, hanging low. There are two purposes of the tail other than looking pretty. First, the tail helps get rid of insects, and it helps the horse steer and has balance when moving.
Cold-blooded horses have coarse, thick tails and mane hair, while hot-blooded equine hair is thin and silky.
The color of a horse’s skin varies based on the color of the hair covering it. You see pink skin on gray horses, while all other colored horses have black or dark gray skin.
The bulb of the heels in the back of the hooves is the most important part of your horse’s skin.
Equine Muscular Structure
Keeping your horse’s muscular structure taut can prevent injury and keep your horse in optimal condition. Pay particular attention to strengthening the back muscles to prevent strain from using a saddle and rider.
Around 700 different muscles in a horse’s bodywork to control the movement of the various bones. These muscles fall into three types – skeletal, cardiac, and smooth.
The skeletal muscles are responsible for supporting the organs and skeleton, controlling moves, helping the body regulate temperature, and protecting joint posture and stability.
Smooth muscles help with digestion and control bowel movements. And the bladder is responsible for involuntary body functions and aid and surrounds the vascular and reproductive systems.
Finally, the cardiac or heart muscles maintain blood flow through the body and help the heart beat 32 to 36 times a minute. These muscles are 1% of the body weight and circulate 40 liters of blood through the body.