Twitch response – firm perpendicular pressure applied over the trigger point can cause a local twitch response.Palpation provokes a characteristic pain referral pattern.Therefore a trigger point is a small specific tight area sometimes referred to as pea shape within a tight band it is not a whole muscle in spasm. A hyperirritable locus within a taut band of skeletal muscle.What makes a trigger point a trigger point? Identifying primary trigger points is the key to treatment success as often satellite trigger points will remain active until the primary trigger point has been deactivated. Satellite trigger points are secondary trigger points that develop within the referral zone of an active trigger point. Primary ones are trigger points that have been activated directly by acute or chronic muscle overload whereas secondary trigger points develop due to the dysfunction caused by a primary trigger point or other somatic or visceral pathology. Furthermore trigger points are divided into primary secondary or satellite points.
Muscles with latent trigger points are often tight and weak and a latent trigger point can develop into an active one. Latent trigger points on the other hand do not cause spontaneous pain but referred pain is elicited on palpation. Often the pain is described as a poorly localised deep radiating ache and movement may sometimes exacerbate symptoms. Active trigger points cause spontaneous pain at rest and palpation of these points causes localised pain and a pain referral pattern similar to the patients’ complaint. Trigger points can be classified as either active or latent. Trigger points are very common and most people develop at least one during their lifetime and certain factors can precipitate and perpetuate there development such as emotional stress, exhaustion and metabolic conditions including hypothyroidism. The severity of the symptoms can vary dramatically both between different patients and overtime in the same patient. Symptoms are usually referred away from the trigger point and the painful area may not even include the trigger point itself. Pain is often dull in nature but it can cause other common symptoms such as tingling and numbness in its referral zone. Both of these result in a small area of damage which is slow to heal and in turn causes persistent pain generation due to the formation of a trigger point. Trigger points can develop after an acute (lifting/carrying something heavy) or chronic (poor posture overload) muscle strain. The pain patterns for most muscles have been well established by Travell and Simons, a common example is the anterior fibres of the upper Trapezius muscles causes neck pain and temporal headaches. Essentially it is a tight area (knot) within a muscle that can cause spontaneous pain referral into a completely different area to where the muscle is. They are defined as a ‘hyperirritable locus within a taut band of skeletal muscle, located in the muscle tissue or its associated fascia’ (Travell and Simons 1983).