WHAT IS A TRIGGER POINT?
You probably know what a Trigger Point is if you have had a massage - they are localised, hyperirritable areas, found within muscles, that are often exquisitely painful on gentle compression. In humans they are known to give rise to characteristic referred pain and can cause changes in internal organ function, as well as focal tenderness (found within a taut band in the muscle), restriction in range of motion of the joints and weakness of the affected muscle. Not all trigger points are perceived as painful (active) and may only be painful with additional pressure (latent). One of the most common trigger points in people is in the trapezius muscle (where a singlet/dress strap would sit on the shoulder). If you press gently on this area and you find a firm area that is tender, you have just found a trigger point.
As well as being a very common cause of stiffness and musculoskeletal pain in humans, they are also commonly found in other animal species, including dogs and cats and often contribute to (or cause) lameness and stiffness. The pain from trigger points varies from being mild and intermittent to being severe enough to cause non-weight bearing lameness.
HOW DO TRIGGER POINTS DEVELOP?
Trigger points are thought to develop in skeletal muscle due to acute overload, overwork fatigue, direct trauma, chilling, as well as secondarily to other trigger points, internal organ disease and arthritis. The localised muscle contracture (spasm) present within a trigger point can persist for months or years after the trigger point has formed.
In dogs and cats, trigger points will often develop after musculoskeletal injury or surgery and in animals with arthritis. Once an animal has recovered from a painful condition or injury, there may be ongoing stiffness or lameness due to unresolved trigger points in the muscles. Trigger points will often occur in all four legs simultaneously (even though they may be causing most pain and lameness in one leg). Trigger point pain is often worse in cold weather and can improve with slight exercise but worsen with more strenuous activity. Stretching of the muscles helps to prevent the formation of trigger points.
HOW CAN TRIGGER POINTS BE DIAGNOSED?
Trigger points can be diagnosed by carefully observing the animal’s gait (shortening of a muscle will lead to a change in posture or movement), gently feeling the muscles for localised areas of firmness or tenderness (often leading to a yelp/jump from the dog, though some animals are very stoic) and testing the ranges of motion of joints. Joints will not move a normal amount in certain directions if the muscles around the joint have trigger points. X-rays and ultrasound are not of use to diagnose trigger points. There is often little or no improvement with pain-killing or muscle-relaxing medication.
Some common trigger points are shown in this illustration.
WHAT CAN BE DONE TO TREAT TRIGGER POINTS?
Many physical therapies are of use in treating trigger points. Treatment normally requires stimulation of the affected area, which causes some relaxation of the trigger point in the muscle, to allow the muscle to be gently stretched to its full length. At Gladesville Vet Hospital the stimulation techniques used include pressure/release massage, transcutaneous electrical nerve stimulation (TENS) and certain acupuncture methods. Gentle warming, massage and stretching techniques are usually shown to the owner to reduce the recurrence of trigger points. Treatment sessions normally last approximately 30 minutes. There is often a good to dramatic improvement in an animal’s lameness after up to four treatments. Maintenance treatments may or may not be necessary depending on the animal’s condition.