Illustration of equine tendons and ligaments
Horse people spend a lot of time and energy thinking about tendons and ligaments. Injuries to these structures can be devastating. What are tendons and ligaments and why are they so important?
A tendon is the end point of a muscle, the structure that attaches muscle to bone. A muscle is divided into 2 parts, each constructed of different material. The fleshy part of the structure is the muscle belly and on either end are tendons. The belly is made of cells called myofibers, cells that are shaped like drinking straws, long and thin. These cells are bundled together in groups called fascicles. Each fascicle is then “wrapped” in a connective tissue covering. Myofibers are the pliable and stretchy part of the muscle that has contractile properties. The belly is able to contract or shorten its overall length to pull bones closer together and create movement. The belly is well supplied with blood and nutrients which speeds healing of injured muscles.
COMMON CAUSES OF TENDON/LIGAMENT INJURY
• Fatigue
• Repetitive over-use
• Insufficient warm-up and cool-down
• Falls, slips
• Hoof imbalances, improper trimming
Tendons are made of dense connective tissue consisting of tough fibers that are aligned in long parallel bundles in the direction of stretch. The connective tissue is composed mostly of collagen fibers. These fibers are very strong, but afford little in the way of give or stretching. Their purpose is to firmly attach a muscle to the bone. Tendons do not have a good supply of blood, so they lack the source of oxygen and nutrients that would allow faster healing.
Ligaments, generally, connect bone to bone. In some instances, they can also help to form an anchor for other structures in the body. Ligaments are also composed of dense connective tissue, but are more elastic than tendons. Ligaments are the structures that hold joints together and provide stability to a joint. They, like tendons, also have very little in the way of blood supply, extending healing times.
In horses, the suspensory apparatus is a group of ligaments in the lower legs that provide support, strength and stability to the area below the knees and hocks. Horses have no muscles below their knees and hocks.
STRAINS AND SPRAINS
The most common injuries to tendons and ligaments are strains and sprains. Less serious is a strain, because there is no tearing of any tissue. The tendon or ligament is stretched or has received some trauma such as a blow from a kick or over-reached step. A strain is characterized by swelling and inflammation which covers a large area on the lower leg. The swelling is spongy and the horse may be slightly lame, but not disabled. Strains generally resolve in several days to a week with minimal treatment such as cold hosing, rest and wrapping in standing bandages.
A sprain is a more serious injury. Here fibers of the tendons and/or ligaments are severely stretched or torn, or the entire structure is completely ruptured. A suspensory injury consists of damage to one or more of the ligaments of the suspensory apparatus (see B in the illustration). A bowed tendon refers to damage of either the deep digital flexor tendon (C) or superficial digital flexor tendon (D). It is more common for injury to involve the superficial tendon. The term “bowed tendon” comes from the appearance of the damaged tissue as it forms a pocket of inflammation that curves outward from the back of the cannon bone. In these injuries the parallel fibers of the tendon/ligament are torn or broken. The appearance is like a rope that is frayed in the middle. Sprain injuries are characterized by firm, dramatic swelling that develops shortly after the injury. The horse will be visibly lame and sensitive to palpation of the area. As mentioned previously, due to the lack of blood supply in these structures, healing times can take anywhere from 6 to 12 months.
Some injuries are hard to avoid. A slip or fall in poor footing, or getting stuck in deep mud can cause leg injuries. Hoof imbalances can place excess strain on the supporting structures. Improper trimming, shoeing or angle changes done too rapidly can overload a tendon or ligament.
The most common cause of injuries is from repetitive overuse. Horses need to be properly conditioned for the activity that is being undertaken. When muscles become fatigued, they lose their elasticity, placing more tension on the tendons and ligaments. Improper or inadequate warm-up can also be a contributing factor. An appropriate warm-up routine increases circulation to the muscles which supplies them with adequate oxygen and nutrients for the work that is to come. The other end of the workout should also include a cool-down routine. The horse should be allowed to return to a resting heart and respiration rate before being put away.
The best medicine for avoiding injuries is to think of your horse as an athlete. Provide your horse with a training routine that would mimic a workout – 10-15 minutes of easy loose rein walking and trotting prior to and after your training session.
Theresa Gagnon is a Certified Veterinary Technician and Licensed Massage Therapist. She is the Director of Animal Programs at the Bancroft School of Massage Therapy in Worcester, MA. Theresa’s specialties include craniosacral fascial therapy for animals. She can be reached at the school www.horseanddogmassage.com or through her own website www.mendingfencesequine.com. Email [email protected]