Every muscle has a different effect at either end. Since some of the muscles that originate at the innominates insert into the extremities, such as the latissimus dorsi into the arm, the adductors and abductors into the femur, and the quadriceps, hamstrings, sartorius, TFL and other muscles into the knee, it may be reasonable to look at the sacroiliac joint in evaluating extremity dysfunctions. Once this relationship is understood, the simplicity of the underlying nutation and counternutation patterns makes complex dysfunctional syndromes more tenable. The roles of more muscles, and their effects on structural distortions, can be recognized within this unifying pattern. Thus, the nutation lesion and its ligamento-muscular response present a unifying concept in understanding, preventing, and treating many musculoskeletal injury and pain syndromes.

Pronation/Supination
Due to the stabilizing effect of muscles such as the piriformis and obturator externus on the sacroiliac joint, the femur is rotated externally. With the femur, the foot rotates laterally at such an angle that normal toe-off may no longer be possible. Instead, push-off stresses the first ray and the medial arch of the foot, leading to excessive pronation. On toe-off, the foot may not lock as it should during supination. As a result, the ligaments supporting the medial arch will undergo micro trauma and may eventually weaken, creating instability and chronic hyper-pronation. The ligamento-muscular response is supination, which may or may not develop into hyper-supination, depending on use and chronicity.

Medial Meniscus
As discussed above, the upper leg rotates laterally, and the foot may undergo excessive pronation during mid-stance. During pronation, the lower leg rotates medially. The combination of an excessive lateral rotation of the upper leg with a normal or excessive internal rotation of the lower leg stresses the knee, potentially placing significant stress on the medial meniscus. Activities that involve bending, lifting, twisting, while placing weight on the side of lesion, will accentuate the rotational stress on the medial meniscus.

Anterior Cruciate Ligament (ACL) Sprains
The ACL is designed to limit excessive knee extension and internal rotation of the lower leg relative to the upper leg. In addition to sprain occurring in extreme hyperextension, the ACL is frequently torn in severe twisting movements of the knee in which the lower leg excessively rotates internally, relative to the upper leg.

I suggest that repeated micro trauma to the ACL is caused by the same mechanism that leads to excessive pronation and medial meniscus stress. Over time, the ligament weakens and becomes susceptible to rupture. This effect can be magnified by improper coordination between muscle groups that move the joint. As one muscle turns off, the next muscle in sequence should turn on in smooth synchronization. This timing is dependent upon reflexes initiated in the ligaments of the involved joints as they respond to pressure changes during movement. Although the initial thought is to look at the attachments of the hamstrings and quadriceps at the knee, it is suggested that their proximal attachments are just as likely to play a key role in their dysfunction. In the sacroiliac nutation lesion, the hamstrings, more so the medial, are inhibited, while the quadriceps and lateral rotators of the upper leg are contracted. Although these muscles are inhibited or contracted to support the sacroiliac joint, their imbalance may significantly delay load transfer through the knee, contributing to excessive lateral rotation of the upper leg and internal rotation of the lower leg. Over time, microtrauma may weaken the ACL and set up the ligament for a single damaging event.

Contralateral Shoulder Dysfunction
With a right sacroiliac nutation lesion, the muscles cause the innominates to rotate to the left. To provide balance, the thoracolumbar spine rotates to the right and laterally flexes to the right. At this point, the righting reflex causes the upper spine to rotate back to the left in order to align C2 over S2 in an upright posture. As a result, we have different influences affecting the spine and shoulders. From below, the body will try to protect the sacroiliac joint but, from above, it is trying to balance the body with gravity. The shoulders rotate with the thoracolumbar spine toward the side of lesion, but this movement is countered by the counterrotation of the upper thoracic spine; while the shoulders are rotating right, the upper spine is rotating left. The counterrotation of the upper and lower spine results in a twisting of the spine, which compacts the rib cage on the upper left and lower right. This compaction will alter the position of the upper ribs and may cause some ribs to shift out of place. The articular processes of the lower thoracic/upper lumbar vertebrae will be prominently posterior on the side of lesion, while those of the upper thoracic vertebrae will be prominently posterior on the contralateral side. This upper thoracic “rib hump” will force the scapula to ride improperly and, in some cases, cause misalignments of the scapuloclavicular and sternoclavicular joints, which may have some bearing on thoracic outlet syndrome and cervical biomechanics. The mechanics of the entire shoulder girdle will be altered. These mechanics are induced by a combination of muscular actions that influence both shoulders in different manners and is a good example of how the SIJ ligaments, when sprained, may cause dysfunction in a distant joint on the opposite side of the body.

See Spinal-Pelvic Syndromes for associations between the Nutation Lesion and:
        -Pelvic Torsion: AS/PI
        -Facet Syndrome
        -Lateral Canal Stenosis with Nerve Root Impingement (e.g. Sciatica)
        -Lumbar Disc Herniation
        -Spondylolisthesis
        -Lumbosacral Hypomobility
        -Anterior Thoracic Vertebrae
        -Scoliosis

In the future, I will describe associations between the Nutation Lesion and the following:
        -Hip Degeneration
        -Patellar Tracking Dysfunction
        -Piriformis Syndrome
        -Sciatica
        -Pudendal Nerve Entrapment
        -Thoracic Outlet Syndrome
        -Spinal Subluxations
        -And more

More research is needed.

References:
1. Bergquist-Ullman, M. and U. Larsson, Acute low back pain in industry. A controlled prospective study with special reference to therapy and confounding factors. Acta Orthopaedica Scandinavica, 1977(170): p. 1-117.
2. Kelsey, J.L. and A.A. White, 3rd, Epidemiology and impact of low-back pain. Spine (Phila Pa 1976), 1980. 5(2): p. 133-42.
3. Panjabi, M.M., A hypothesis of chronic back pain: ligament subfailure injuries lead to muscle control dysfunction. European Spine Journal, 2006. 15(5): p. 668-76.
4. Lovett, R., The Mechanism of the Normal Spine and its Relation to Scoliosis. Boston Medical and Surgical Journal, 1905. CLIII(13): p. 349-358.