Where either movement impairments (characterised by pain avoidance behaviour) or motor control impairments (characterised by pain provocation behaviour) represent the predominant mechanism underlying the pain disorder (O’Sullivan 2005), physical therapy (myotherapy) interventions may lead to positive outcomes.
Patients present either with an excess or deficit in spinal stability (Panjabi 1992).
The stabilisation of the sacroiliac joints can be increased in two locking mechanisms (Vleeming 1990):
- Form closure describes the structural fit of the sacrum and ilia.
- Force closure describes the dynamic action of the ligaments, muscles, and fascia supporting the pelvis.
Muscle weakness and insufficient tension of ligaments can lead to diminished compression, influencing load transfer negatively.
Gait is the default pattern of human movement and involves the shoulders counter-rotating with the contralateral hips to create efficient movement.
The posterior oblique sling consists of: gluteus maximus, latissiumus dorsi, and contralateral thoracolumbar fascia (TLF).
The anterior oblique sling consists of: pectoralis major, external abdominal oblique, contralateral internal abdominal oblique, transverse abdominis (TVA), adductor-abdominal fascia, and contralateral adductor longus. When this group of muscles contract together, it compresses the entire pelvic girdle, and provides force closure of the symphysis pubis.
The deep longitudinal sling consists of: tibialis anterior, fibularis longus, biceps femoris (BF), gluteus maximus, sacrotuberous ligament (STL), thoracolumbar fascia (TLF), and the contralateral erector spinae and contralateral multifidus. The contraction of the muscles in this sling triggers a series of actions which encourage the sacroiliac joint into its stable closed packed position. The pull on the sacrum through the erector aponeurosis reinforces the stable closed packed position. The deeper fibres of the multifidus contract to increase segmental stability through compression. Both the erector spinae and the multifidus muscles lay enclosed in a fascial envelope created by the thoracolumbar fascia system. When these muscles contract, they have a broadening effect (inflation of the fascial cylinder) which will further increase tension and assist with force closure.
The lateral sling consists of: gluteus medius and minimus, tensor fascia lata (TFL), iliotibial band (ITB), adductors, and contralateral quadratus lumborum (QL). The lateral sling is used in coronal plane stability and is involved in pelvo-femoral stability in dynamic movements such as gait, lunges and stair climbing. The gluteus medius and minimus are hip abductors and medial rotators whilst the TFL works in synergy with these muscles to hold the pelvis level in single leg movements. Additionally, the TFL works with the gluteus maximus on the ITB to stabilise the hip joint by holding the head of the femur in the acetabulum. The lateral sling comes into tension to maintain pelvo-femoral stability. Failed control by the lateral sling often presents as a hip drop (positive Trendelenburg sign) during the stance phase of gait and single leg stance.
For more information: Fascia & Tensegrity