Excerpted from Page, Frank, and Lardner. Assessment and Treatment of Muscle Imbalance: The Janda Approach (2010)
Articular chains result from the biomechanical interactions of different joints throughout a movement pattern. There are two types of articular chains: postural and kinetic.
Postural chains describe the position of one joint in relation to another when the body is in an upright position. They influence positioning and movement through both structural and functional mechanisms.
Structural mechanisms describe the influence of static skeletal positioning on adjacent structures. Structural chains are influenced by static joint position.
The most recognized structural postural chain occurs throughout the spine. The postural position of the cervical, thoracic, and lumbar spine is typically assessed in patients with musculoskeletal pain. As depicted in the Brugger cogwheel chain mechanism of poor posture, poor posture is a chain reaction occurring throughout the spine from the position of the pelvis to the position of the head.
Poor sitting posture (left) results in a posterior pelvic tilt. This is indicated by a counterclockwise cogwheel and indicates a reduction in the normal lordosis of the lumbar spine. This reverses the normal kyphosis of the thoracic spine through a clockwise cogwheel, and then creates a counterclockwise rotation in the cervical spine resulting in a forward head with an extended neck…a typical example of poor posture.
To assume proper posture (right), reverse the lower cogwheel (clockwise) to rotate the pelvis anteriorly. This in turn rotates the middle cogwheel (counterclockwise) lifting the chest upward while rotating the upper cogwheel (clockwise) stretching the neck and repositioning the head.
Functional mechanisms describe the dynamic influence that the position of the keystone structures (pelvis and scapulae) has on the muscles attaching to those structures. Functional chains are influenced by muscular activity around joint structures.
In a functional postural chain, the postural position of keystone structures contributes to pathology and dysfunction. Keystone structures (pelvis and scapulae) serve as attachment points for groups of postural muscles. Muscle tightness or weakness may be caused by, or be the cause of, altered postural positioning. The position of these structures is a key in assessment of posture and in the role these structures play in dysfunction.
For instance, the pelvis can influence the position of the adjacent lumbar spine. It can also influence the length-tension of muscles originating from the pelvis, such as hip flexors and hamstrings.
The left image shows a balanced pelvis in the neutral position. In the middle, we see a posteriorly rotated pelvis with short/tight hamstrings and overstretched/weak hip flexors. On the right we see an anteriorly rotated pelvis with short/tight hip flexors and overstretched/weak hamstrings.
Kinetic chains are most often recognized as the concepts of open and closed chain movement patterns, in which the focus is on the movement of joints.
These chains can be easily identified through biomechanical assessment, such as gait assessment. For example, a chain reaction of the lower extremity during gait is well known; foot pronation causes tibial internal rotation, which causes knee valgus and hip internal rotation.
This chain reaction can often translate to some or all of the following muscle impairments: ipsilateral (same side) short/tight peroneals, overstretched/weak tibialis anterior; possible pes planus or plantar fasciitis; short/tight hip adductors, short TFL; overstretched/weak hip abductors, tight ITB, possible lateral knee pain.
Clearly, clinicians must look away from the site of the pain for the possible biomechanical contributions.