The kinetic chain is a chain of joints and other body tissues that act together. Really, you can consider each limb on your body, and the joints which attach those limbs to the spine, as kinetic chains. According to Steindler (1955), the kinetic chain is “a combination of several successively arranged joints constituting a complex motor unit“.
“The kinetic chain is made up of the soft tissue system (muscle, ligament, tendon and fascia) neural system and articular system.”
Three factors are required for the kinetic chain to work properly:
1. Normal length-tension relationship – this means that the length and tension of the muscles and ligaments in the kinetic chain must be normal and in proper relation to each other.
a. When the biceps contract, the triceps must relax. Altered length and tension in those muscles will create imbalance and dysfunction. If the hamstrings are too tight, this will alter the way the knee works. Tight ‘pecs’ (pectoralis muscles in the upper chest) will cause problems in the shoulder joint.
2. Normal force-couple relationship – force-coupling maintains anatomy in proper position despite the forces acting on them.
a. When the shoulder muscles are working the humeral head stays in the glenoid fossa due to the rotator cuff muscles holding the humerus in. Without these coupled forces the muscles working the arm could displace the arm in the shoulder.
3. Normal arthrokinematics – this is the proper relationship of opposing joint surfaces involving proper “roll”, “spin”, and “slide” actions to allow for proper motion. This helps prevent deformation of the joint.
a. If a joint surface is degraded, for example when the hips or knees develop arthritis, this affects how the two opposing bones can interact at the joint. If any one of these three things is not working correctly, all three will be compromised.
These three altered relationships always occur together. You cannot have only an abnormal length-tension relationship, but have a normal force-couple relationship. If one is altered, all three will be altered. The proper function of these three factors allows for optimal sensorimotor integration, neuromuscular efficiency, and tissue recovery.
Muscles function as levers on bone. A contracting muscle will bring two bones closer together. The body creates movement by activating a series of levers with more force in larger and less force in smaller segments, in order to summate velocity and reduce force applied to smaller, distal segments. These links must be moved in specific sequences to allow efficiency. Generally, this is organized proximal to distal (from near the center of the body towards the hands and feet).
The body needs proximal stability to have distal mobility. For example, an unstable cervical spine (neck) will disrupt the body’s ability to properly utilize the wrist. A more complicated example is a baseball pitcher throwing a pitch. Stability is required in a kinetic chain ranging from the feet to the hands. In this example the feet must firmly be planted on the ground, the legs must pass force through the knees and hips, through the trunk and spine, across the shoulder joint, through the elbow and ultimately to the wrist. Dysfunction from a missing link or improper timing will lead to greater force at distal segments.
There are two basic types of functional chain deficits:
1. Anatomic – related specifically to the area of injury (ex. rotator cuff tear causing diminished shoulder function, or torn medial meniscus with a resulting “locked” knee). This is the result of overt injury.
2. Functional – can occur throughout the body due to anatomical deficit or actual tissue injury, and can be addressed by chiropractors more readily than anatomical deficits. These often occur due to sub-clinical tissue injury (minor injury).
A properly-trained chiropractor with an understanding of these concepts can recognize and address kinetic chain deficits like the type described in this article.