Page 610 - The Veterinary Care of the Horse

the nerves at specific points along these lines with an acupuncture needle causes changes to

occur within the body.
VetBooks.ir The shortened muscle or myofascial pain syndrome

Many horses are chronically stiff and sore because they have myofascial trigger points in

their muscles. (Myo = muscle, fascia = the dense white fibrous tissue that surrounds
muscles.) Myofascial trigger points (MFTPs) are small, circumscribed exquisitely tender

areas that may be found in taut bands within a muscle. They may develop from:
• a direct injury

• chronic over-use of a muscle

• chilling
• repeated microtrauma (repetitive strain injury).

They are classified as active if they hurt all the time or latent if they are painful only when
pressure is applied. Firm pressure over any trigger point may cause the muscle to jerk

involuntarily. This is known as the jump sign and it happens because the nerve endings in
the muscle have become abnormally sensitized. These trigger points cause chronic muscle

pain in horses and are very commonly found in the lower neck, the abdominal wall, the
hindquarters and the hamstrings. They cause muscle shortening which is not under voluntary
control. This myofascial pain syndrome is responsible for many of the chronically sore backs

we see in horses.

The pain experienced by the horse has several characteristics:
• it often develops days or weeks after the original injury appears to have healed

• it can manifest as a deep aching pain or a brief powerful shooting or stabbing pain

• if left untreated, mild stimuli to the affected muscle can generate extreme pain out of all

proportion to the stimulus.

Unfortunately it does not end there because pain may be experienced elsewhere in the body
due to the muscle shortening. Shortened muscles:

• limit the range of movement of a joint; the horse’s gait will become increasingly short

and choppy
• may pull on their tendons and their attachments causing tendonitis and tenosynovitis

• can lead to increased pressure on the cartilage of joint surfaces, thus the chronic pull of