These muscles include:
- The piriformis muscle
- The upper and lower gastrocnemius muscles
- The square femoris muscle
- The internal and external obturator muscles
1- gluteus maximus muscle (cut)
2- gluteus medius muscle (sectioned)
3- gluteus minimus muscle
4- piriformis muscle
5- superior twin muscle
6- internal obturator muscle
7- inferior twin muscle
8- quadratus femoris
9- sciatic nerve
10- small sciatic notch
11- sacrospinous ligament
12- large sciatic notch
The piriformis takes its medial insertions on the internal face of the sacrum, crosses the greater sciatic notch and is inserted laterally on the greater trochanter. The other rotators all insert laterally on the greater trochanter. The 2 twins and the femoral square are inserted, medial, on the ischium. The obturator internus inserts medially on the medial aspect of the obturator membrane and on the edge of the obturator foramen. The external obturator (not seen in the diagram) inserts on the external face of the obturator membrane and on the edge of the obturator foramen.
All the muscles have a role of external rotator whatever the position of the hip. The piriformis has a role of hip abduction at 90 degrees.
The piriformis, as we will see later, can lead to compression of the sciatic nerve. There are also 4 anatomical variations in the relationship it has with the sciatic nerve:
1- the sciatic nerve passes in front of the piriformis in its entirety (85% of subjects)
2- the peroneal part of the sciatic nerve makes a loop above the piriformis and then passes behind (2-3% of subjects)
3- the peroneal part of the sciatic nerve passes through the piriformis muscle (10% of subjects)
4- the entire sciatic nerve passes through the piriformis muscle (<1% of subjects)
Myofascial syndrome of the piriformis muscle and short lateral rotator muscles
The piriformis muscle
The piriformis muscle can be the seat of trigger point but also be responsible for compression of the sciatic nerve.
Referred pain related to myofascial syndrome affects the sacroiliac region, the buttock, the posterior part of the hip and the posterior part of the thigh:
sometimes the pain may radiate into the inguinal fold and the coccyx. Visceral pain is sometimes described with pain in the rectum during defecation.
Symptoms are aggravated by sitting. Sexual disorders are also described with dyspareunia in women and impotence in men.
The appearance of the myofascial syndrome of the piriformis is favored by the position of the knees apart for a prolonged period (gynecological or urological surgery for example, coitus, etc.)
Standing with repeated rotational movements of the pelvis can also trigger this syndrome.
This syndrome is also favored by body asymmetry:
- Lower limb length inequality
- Small hemi-pelvis
The pain related to nerve compression more or less frankly reproduces sciatic topography pain: buttock, posterior part of the thigh, posterior and lateral part of the leg, foot. Sometimes this attack manifests itself through ataxia (affecting the deep sensitivity of the sciatic nerve). The topography of the sciatic attack can be variable, depending on the local anatomy of the piriformis and the sciatic nerve (see the anatomical diagram above)
Anatomically the pudendal nerve is very close to the sciatic nerve at the level of the ischial spine. Compression of the latter is also possible with related neuralgia of the pudendal nerve.
The examination of the patient looks for painful points on the path of the piriformis. A test in a seated position where the patient tries to spread the knees against resistance can reveal a unilateral weakness of this gesture.
The patient in supine position presents a spontaneous external rotation of the foot of more than 45 degrees.
The patient in lateral decubitus hip flexed at 90 degrees tries to lift his knee against resistance. The gesture is difficult, it can reproduce the patient’s pain and sometimes reveals sciatic involvement (symptom of sciatica)
Ischemic compression techniques are used on the external part of the pyramidal via an external approach. These compression techniques can also work well intra rectally on the medial part of the muscle.
Stretching is performed in lateral decubitus, hip flexed with a downward movement of the knee towards the plane of the table
Sometimes, in cases of nerve compression, decompression surgery is helpful. Tests by infiltrations under scanner can make it possible to specify the attack to see to make the treatment.
The patient presenting this syndrome must, if he sleeps in lateral decubitus, place a cushion between the two knees which limits the tension of the muscle and avoids “difficult nights”.
Likewise, during physical activities (work, gardening, etc.), he must avoid repeated or blocked lateral trunk rotation positions.
The internal and external obturator muscles
The subject of these muscles is covered in “Myofascial Syndrome of the Pelvic Floor Muscles”.
The gastrocnemius and quadratus femoris muscles
Unlike the piriformis muscle, they have been little studied. It gives pain in the lateral part of the buttock and the greater trochanter.
Their treatment is similar to that of the piriformis muscle for stretching. Ischemic compression is done in the painful area near the trochanter