Tendons and Ligaments (to avoid injury and prevent lameness) - Part 1 of 2

Soundness Related - Vital Connections


Fibrous bands of connective tissue that connect bone to bone, ligaments control range of movement and are found throughout the body including the spine, pelvis, hip, stifle and limbs.

Vital Connections - This information is an excerpt taken from an article by Gillian Higgins the creator and founder of Horses Inside Out. To see the complete article or for more information on Gillian's amazing work see the link below.
Connective tissue is composed mainly of cells, fiber and collagen, a fibrous protein - white fibers are relatively inelastic, yellow fibers have the ability to stretch. Most ligaments are mainly white fibers, through capsular ligaments in ball and socket joints have e larger proportion of yellow fibers to allow for a range of movement.

* Ligaments stabilize, protect, support and prevent joints from over-extending, over-flexing or over-rotating.

* Ligaments are formed from strands of collagen that criss-cross and overlap. This makes them stronger and less elastic than tendons. Like tendons they are susceptible to injury and when they do become strained, their limited blood supply makes them slow to heal.

* If they are overstretched or injured, the joint becomes weaker as the elongated ligaments are unable to properly support it.

Tendons - Go Faster Fibers
The horse has no muscles below the knee or hock. This makes the limbs lighter and enables the horse to move faster and more efficiently. As movement in the joints from the elbow down and stifle down is only in the forward and backwards plane, the tendons in the lower leg are either extensors or flexors.

Healthy tendons are well defined and feel firm. Tendons in younger horses appear to be more robust than in mature horses. The digital and extensor muscles and tendons come into play during the latter part of the swing phase of the stride. They help position the hoof ready for impact and weight bearing.

The digital extensor muscles and tendons operate whenever the horse picks up and flexes his fetlock and pastern joints for example when jumping and during the part of the swing  phase in walk. By using elastic recoil during the faster paces, tendons save energy and create movement without the parent muscle having to work hard.

* Tendons are fibrous cords of connective tissue that connect muscle to bone.

*Tendons are formed when the muscle bulk tapers into dense, longitudinally arranged, parallel bundles of collagen, which have high tensile strength allowing them to withstand enormous loads.

* The collagenous fibers within tendons are arranged in a slightly zig-zag or crimped pattern, which allows them to stretch and recoil by approximately 4%. Beyond this stretch limit damage will occur.

* New collagen is produced from cells called fibroblasts, which are interspersed between the collagen fibers.

* Old collagen is constantly being replaced by new fibers. The entire tendon is replaced every six months.

* Where a tendon crosses a joint, it is protected by a synovial sheath and supported by an annular ligament.

* As there are no capillaries within tendons, poor blood supply makes them slow to heal.

Energy-Saving Mechanism
The role of the suspensory ligament, which runs down the back of the lower leg, is to support and stabilize the fetlock. Although it is made up predominately of collagen fibers there are some residual muscle fibers. These, together with its higher proportion of yellow fibers, give the ligament its ability to stretch.

Due to their high elastic fiber content, the suspensory ligament and the superficial digital flexor tendon (SDFT) work closely together as a muscle energy-saving mechanism, particularly at faster speeds when carrying more weight or jumping.

Most weight is taken on the trailing forelimb as this lands first and is perpendicular to the ground. When landing from a fence, the suspensory ligament and the SDFT stretch to absorb upwards of 2 1/2 times the horses body weight. As the body rolls over the planted limb, the fetlock joint extends, putting enormous strain on the fetlock suspension system. At this moment there is hyper-extension of the fetlock and carpal joints. Just like a taught elastic band, when pressure is released from the suspensory ligament and the SDFT, they spring back to their original length. This helps to pull the fetlock joint back towards a flexed position. As the forelimbs snap up, they are almost instantaneously replaced by the hind feet.  

Read the complete article here:
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