The piriformis muscle is a small muscle deep to glute max and lies over top of the sciatic nerve. It originates on the anterior sacrum, and inserts on the greater trochanter of the femur. It’s main action is to laterally rotate the femur. When trigger points developed in this muscle they will refer pain into the sacro-iliac region, across the posterior hip and down the leg. This muscle can also be a cause of sciatic nerve irritation if it gets tight, causing “sciatica” symptoms. 
Volleyball
Trigger points in the gluteus minimus
The gluteus minimus is a small but important muscle that lies deep to the gluteus medius. It originates on the gluteal surface of the ilium, and attaches on the greater trochanter of the femur. It’s main actions are to abduct and medically rotate the hip. Trigger points in this muscle refer pain into the buttock and down the lateral and posterior leg, mimicking sciatica. This muscle should be the first to be examined if a straight leg test turns out negative. 
Trigger points in the gluteus medius muscle
The gluteus medius muscle plays an important role in hip and pelvic stability. It originates on the gluteal surface of the ilium, deep to the gluteus Maximus. It inserts on the greater trochanter of the femur. It’s main actions are to abduct the hip and to assist in internal rotation of the hip. It also maintains pelvic stability during walking and running. Trigger points in this muscle will refer pain into the sacrum, the iliac crest, and down the lateral hip and into the thigh. This muscle is often a cause of lower pack pain.
Trigger points in the gluteus Maximus
The gluteus Maximus is the buttock muscle. It originates on the gluteal surface of the ilium, lumbar fascia, sacrum and sacrotuberous ligament. It inserts on the gluteal tuberosity of the femur and the iliotibial tract. Extension and lateral rotation of the hip are it’s main actions. This muscle is heavily involved in activities like ice skating and is a common area to develops trigger points. When trigger points do develop they can refer pain in a crescent pattern from the gluteal fold to the sacrum. Trigger points can also refer pain deep into the buttock itself making it feel like other deeper muscles are involved. These symptoms can sometimes be mistaken for s.i. Joint problems. 
Trigger points in the infraspinatus
The infraspinatus muscle is one of the muscles that makes up the rotator cuff. It originates on the infraspinous fossa of the scapula, and inserts on the middle facet of the greater tubercle of the humerus. It functions to externally rotate the humerus and to stabilize the head of the humerus in the glenoid cavity during upward movement of the arm. Trigger points in this muscle refer pain deep into the anterior shoulder joint and down the anterior arm. Trigger points near the lower medial border refer pain into the rhomboids. This muscle is often injured during throwing motions.
What is a trigger point
Dr Janet travel coined the term trigger point in 1942 to describe clinical findings with characteristics of pain related a discrete irritable point in muscle or fascia that was not caused by acute trauma, inflammation, degeneration, neoplasm or infection. The painful point can be palpated as a nodule or tight band in the muscle that can produce a local twitch response when stimulated. Palpation of the trigger point reproduces the pain and symptoms of the patient and the pain radiates in a predictable referral pattern specific to the muscle harbouring the trigger point.
Aberdeen Chiropractic 