Biomechanical Aspects of Joint Hypermobility

The Joint Hypermobility Syndrome affects articular biomechanics in many ways. These influences are presented and discussed in this chapter. Joint hypermobilityJoint hypermobility \i alters the biomechanics of the locomotor system due to ligament failure, a lack of adequate tension for the promotion of stability. There is decreased strength, fatigue and muscle weakness. These manifestations interfere with the stability of the vertebral bodies, both statically and dynamically. The rangeRange \i of motion in any jointJoint \i depends on a variety of factors, including muscle tone, elasticity of ligaments and joint capsules, and the shape of bone contours. Bones provide mechanical support through a framework consisting of a collagen matrix on which calcium salts are deposited and this is responsible for their strength. The tendon is a fibrous structure that transmits muscle strength and generates movement, while ligaments are the bundles of resistant fibers, which are fundamental in controlling movement by promoting stability to the jointJoint \i. Stability of a ligament is obtained by the strength and elasticity of the collagen, which varies between individuals according to the inherited collagen structure. The human body adapts to many different situations. The evolution of body movements, with their specific functions, occurs as a consequence of adaptive mechanical responses from the musculoskeletal system tissues. It is a natural interaction of form and function and can be defined as a modification of an organism or its parts, which makes it more suitable for existing in its environmental conditions. In this way, bones are also subjected to the adaptive characteristics of loads and forces that are imposed upon them throughout skeletal development. Adaptation of skeletal muscles occurs by passive and active adjustments of forces for the effective muscle activities of contraction and relaxation. The combination of these mechanical properties and the behaviour of musculoskeletal tissues is relevant to the understanding of the mechanical functioning of jointJoint \i mobility. In this context, biomechanical studies indicate that all human body movements are a result of the orchestration of forces around joints and that the architectural body frame displays a physiological response to these forces. Just as anatomy is influenced by mechanical force, gravitational force also influences musculoskeletal architecture.