Tendons

1. Tendons connect muscles to the bone to move bones whilst ligaments connect bone to bone and serve to stabilise structures such as the knee.
2. Both tendons and ligaments are composed mainly (60-80%) of collagen and elastin which are purely structural, not live tissue.
3. The living cells in tendons are known as tenoblasts and tenocytes.
4. Tendons have a very poor blood supply. Combined with a low number of live tendon cells, this is partly why tendon injuries are often slow and poor to heal.
5. The largest tendons in the horse’s forelimbs as the SDFT (Superficial Digital Flexor Tendon) and DDFT (Deep Digital Flexor Tendon).
6. The SDFT is also one of the longest tendons in the horse’s body.
7. Tendons are essentially large rubber bands. When stretched and released they generate heat.
8. During exercise, tendons can also stretch and retract between 2 to 8cm.
9. During galloping, the temperature within the core of large tendons can be similar to those within the muscles (44°C or more).
10. Heat within tendons can damage and kill tendon cells, leading to inflammation. Inflammation in turn leads to damage and weakening of the tendon. Over time this weakens the tendon eventually leading to failure and a tear or rupture.
11. The SDFT is very near the surface and is only covered by a very thin layer of skin and fat and the the reason why protective boots are advisable for jumping or fast exercise in particular where there is a high risk of interference/brushing or over-reaching.
12. The majority of tendon injuries are caused by the long-term accumulation of small amounts of damage rather than a single isolated severe injury.
13. Most tendon injuries occur in the forelimbs.
14. In elite showjumpers, elite eventers and National Hunt racehorses the risk of injury to the SDFT is very high compared with Flat racehorses and elite dressage horses.
15. When tendons are damaged, tenoblasts are more involved in the tissue repair process, depositing collagen fibres.
16. During the period of each stride when each limb is on the ground, energy is stored within the limb’s tendons and a significant amount is used in the next stride. This is one of the main reasons horses have such a high athletic capability.

We have lots of articles and information about equine tendons including:

• Research Paper PrePrint – Evaluation of the Cooling Efficacy of Different Equine Leg Cooling Methods
• Webinars – Boots And Bandages – Know The Facts – A Three-Part Series By Dr David Marlin
• Article – Roadwork – Some things to consider!
• Article – Should ice just be for our Gin & Tonic?
• Article – Tendon firing and blistering – a review of the evidence for and against its continued use in horses