10/13/2026
DID YOU KNOW THE SUSPENSORY LIGAMENT OFTEN CONTAINS MUSCLE FIBRES?
One of the fascinating things I regularly come across during equine dissections is the presence of muscle fibres within the suspensory ligaments on the proximal branch near its Origin.
Many people assume the suspensory ligament is simply a thick band of collagen fibres, but anatomically, it’s much more complex than that!
The equine suspensory ligament is actually a highly specialised structure that evolved from the interosseous muscle. Although it has become predominantly ligamentous to support the weight of the horse, it still contains varying amounts of skeletal muscle fibres, fat, blood vessels and nerves.
Research has shown that the amount of muscle tissue varies between horses, breeds and even with age. Interestingly, some studies have found that these muscle fibres are predominantly slow-twitch fibres, suggesting they may have a functional role rather than simply being evolutionary leftovers.
SO WHY DOES THIS MATTER?
I had an interesting conversation with veterinarian Dr Henk Offreins from Equine Tendon yesterday about the possibility of proximal suspensory injuries being overdiagnosed through ultrasound, and whether corticosteroid injections are sometimes being used unnecessarily. A light bulb went off in my mind because I see muscle fibres in the upper suspensory branch regularly.
This sent me down a research rabbit hole!
Studies comparing ultrasound images with MRI and histology have demonstrated that normal muscle and fatty tissue within the proximal suspensory ligament can appear as darker areas on ultrasound, potentially resembling lesions.
In other words, what appears to be damaged tissue on an ultrasound may sometimes be perfectly normal anatomy!
Of course, ultrasound is an incredibly valuable diagnostic tool, and genuine suspensory injuries absolutely occur. But research also highlights the importance of understanding normal anatomical variation before interpreting every abnormal-looking area as an injury.
This brings us to another interesting question.
ARE WE SOMETIMES TREATING WHAT ISN’T ACTUALLY BROKEN?
Corticosteroids are commonly used in equine veterinary medicine to reduce inflammation and pain, but they do not repair damaged collagen fibres. There are also concerns about their potential effects on connective tissue healing, depending on how and where they are administered.
There isn’t currently enough evidence to conclude that steroids are routinely being overused for proximal suspensory injuries. However, it does raise an important question about ensuring we have an accurate diagnosis before deciding on treatment.
An ultrasound finding alone doesn’t necessarily tell us whether tissue is damaged, whether that finding is responsible for the horse’s pain, or whether corticosteroids are the appropriate treatment.
THIS IS WHY ANATOMY MATTERS!
The more time I spend dissecting horses, the more I appreciate just how complex their bodies really are. Structures we often describe in simple terms are frequently far more intricate than we realise.
Dissection gives us an opportunity to see the tissues themselves, understand their relationships and question some of the assumptions we make about how the equine body works.
I’m certainly not suggesting veterinarians are routinely getting these diagnoses wrong. What I am suggesting is that we should remain curious, continue questioning and use the growing body of scientific research to improve our understanding.
Because ultimately, better anatomical understanding leads to better decisions for our horses.
Some interesting scientific studies if you’d like to read further:
* Bischofberger et al. (2006) — MRI, ultrasonography and histology of the normal suspensory ligament origin.
* Soffler & Hermanson (2006) — Muscular design in the equine interosseus muscle.
* Werpy et al. (2013) — Comparison of ultrasound and MRI of the normal proximal suspensory ligament.
* A Review of the Equine Suspensory Ligament: Injury Prone Yet Understudied (2025).
The more we learn, the more we realise how much there still is to understand. The is where dissection work fits in so neatly to science. We see patterns and this creates conversations. Huge thank you to Equi-ed who make it possible for me to fly to the other side of the planet to have these conversations with people at the coal face of change.
Photo below showing the lateral side of the proximal suspensory branch, a few centimetres below the origin.
