Equine anatomy doesn’t need to be complicated and learning as much as you can about how the horse moves and functions will help you to become a more effective and sympathetic rider and trainer. In this series of articles, we aim to clarify some of the most common misconceptions and focus on the facts in a clear and easy to understand way.
In this second article of our series exploring anatomical misconceptions, we are looking at the location of the hip joint and hindlimb anatomy, and how it impacts the horse’s training.
“I think this misconception comes from the fact that as human beings, our legs, which are equivalent to the horse's hind legs are vertical,” suggests Gillian. “When we look at our own femur (thigh bone) this bone is vertical. Then, moving down to the knee, and the tibia and fibula, these two bones in our lower limbs are also vertical. Many will assume that the bones in the horse’s limbs are going to be more upright and closer to the vertical than they are.”
The Position of the Hip Joint
The actual position of the hip joint is another common misconception. When asked where it is, many will point to the false hip (tuber coxae) rather than the location of the hip joint itself.
The false hip is the widest part of the pelvis. Here comes another misconception - the pelvis isn’t one bone, it’s made up of three bones – the ilium, ischium, and pubis which are fused together.
There are three parts of the pelvis that you can feel from the outside of the horse
The highest part is the tuber sacrale or the point of croup
The widest part of the pelvis is called a tuber coxae and this creates the false hip
The tuber ischium, this creates the point of buttock. If you run your hand down the hamstrings, you can feel a slightly harder part, this is the tuber ischium – this is equivalent to our seat bones.
Finding the Hip Joint
Now you know a bit more about the pelvis, we can locate the hip joint. If we were to draw a line from the false hip towards the tuber ischium (point of buttock) the hip joint is approximately two thirds of the way forward from the tuber ischium.
Run your hand between these two points and you will bump over a slightly harder part, this is not the joint itself that you are feeling but a bony projection that's opposite the location of the hip joint. This is called the greater trochanter of the femur. Running over the top of that there’s some gluteal muscles and the biceps femoris, so where you feel the greater trochanter, the hip joint is directly underneath.
The Function of the Hip Joint
The hip joint is a ball and socket joint and allows the horse to swing his hindlegs both forwards and backwards, but also side to side in the form of abduction and adduction - this means taking the limb towards and away from the body and we see this movement when the horse performs lateral work such as leg-yield or half-pass.
The hip joint also allows for rotation, and we see this when a horse is turning, in particular, if a horse has got his foot on the ground, and twists there'll be some rotation happening within the hip joint.
The hip joint gives the hind limb a good range of movement and this is important because from the stifle down, the horse doesn’t have the ability to laterally flex or actively abduct or adduct his joints. It’s the hip joint that is responsible for creating the sideways movements within the hindlimbs.
Why is the hip joint position where it is?
To answer this question, we need to go back to look at the angles within the bones. The hip joint is positioned two thirds of the way along the length of the pelvis and then it angles forward to the upper hindlimb bone (the femur), which is the bone within our thigh.
Next, we have the stifle, which is equivalent to our knee, the bone (the tibia) from that point angles back again towards the hock (these bones are equivalent to the tibia and the fibula in our lower limb, so basically our shin bones). Interestingly, the tibia in the horse is very large, and the fibula is very small - it's about the size of a splint bone and is usually fused to the top of tibia. This is very different to humans where both the tibia and fibula run the full length of our lower limb from knee to ankle. The horse's hock joint is equivalent to our ankle, and the bones below the hock are equivalent to the bones in our foot.
If the horse was standing, as we do, they would be standing on the area between the hock and the fetlock.
If we were to stand like a horse, we would find that the angles of our bones would be like standing in a squat position. This would be really hard work for us because we're designed to stand with our femur, tibia and fibula virtually vertical, whereas a horse is much more angled.
The horse also has a very clever system of soft tissue structures, particularly the stay apparatus. Made up of ligaments which includes the suspensory ligament, the reciprocal apparatus, peroneus tertius, superficial digital flexor tendon and other muscles make it easy for the horse to stand naturally with these angles within their bones.
It's these angles of the hind limb bones that make the horse such an athlete and much more capable of jumping than we are! Most horses can jump bigger fences than most human beings and that's partly because of the angles within their hind limbs. If the hip joint was located where many people assume it is (at the false hip), the horse wouldn't be able to perform in the way he does.
How does the position of the hip joint affect the way I ride, train and care for my horse?
Understanding where the hip joint actually is has a big impact on the way we ride and train. If you visualise the hip being in the location of the false hip, you would assume that the hind leg could swing much more easily underneath the horse’s body, but that’s not the case. Thinking the hip joint is where the false hip is and you will expect impossible movement from the horse.
Knowing that the hip joint is in fact positioned further back gives the horse a better ability to basically do squats, and from that position have the ability push forwards. If you truly get the horse to use his hind legs properly, it will affect the position of the back, the outline, how he moves and improve all round way of going.
It’s important when you are training horses, that you don’t just focus on performance, but with longevity in mind too. If you train your horse to go correctly, the forces within his body will be more evenly distributed meaning there is less force on specific structures.
If there is an imbalance in the way of going or if the horse is going with poor posture or not correctly using his hind end, certain structures within the body have more force going through them, and some will have less. This means that in those structures that have a lot of force going through them repeatedly are at greater risk of repetitive strain injury.
“I’m sure many of you will have hear your trainer said to you, forget about the front end and make sure the hind end is working properly and then everything will come right and this is so true. The action and the positioning of the hind end will have an affect the back, forelimb and neck positioning as well.”
Visualising where the hip joint is and the angles of the hindlimb bones will help you as encourage the horse to shift his weight back onto the hindquarters. This increases the angle between the pelvis, the femur, and the tibia and that's going to require more muscular strength, but we need to be able to visualise the anatomy correctly to achieve this correct way of going.
Online Learning
If you've enjoyed this article and keen to discover more about the anatomy and biomechanics of the hindquarters of the horse, there are two must watch on-demand recorded webinars available from the Horses Inside Out Academy.
This on-demand webinar is a must for anyone wishing to improve the strength, action and posture of the hindquarters. It's full of ridden, in-hand and Pilates-style exercises that you can do with your horse to improve his collection and engagement.
Learn about the anatomy, biomechanics and connections of the hindquarters and back that every rider and coach wishing to improve collection needs to understand.
Also, understand how and why poor collection can potentially increase the risk of injury.
Discover how to:-
Assess collection and engagement
Consider strength vs weakness
Recognise good and poor posture and how to improve it
This detailed online lecture demonstration looks at the anatomy and biomechanics specifically related to dressage. It covers many topics including - how the horse maintains an outline, the different head and neck positions and how they affect movement and way of going. Also, understand what is the correct way of going for improving posture and musculoskeletal health, the importance of the base of the neck, the positioning of the hind limb relating to the sacroiliac joint and lumbosacral junction, and how this is important for collection and engagement.
Also, why not come along to one of our live painted horse lecture demonstrations to see first-hand the world of equine anatomy brought to life in a fun, interactive and entertaining way. You will also come away with a host of new exercises to try on your own horse to boost his comfort and way of going.
Our next live painted horse lecture demonstration is at Moulton College, Northants on Saturday 21 September 2024. Tickets are on sale now!