In classic anatomy, ligaments are defined as fibrous bands of dense connective tissue that attach bones to each other - that is, ligaments hold joints together. Ligaments are composed primarily of collagen bundles in parallel, with a mixture of elastic fibers and fine collagen fibers interwoven. This arrangement creates tissue that is pliable enough to allow freedom of motion at the joint and strong enough to resist stretching forces.
Ligaments are traditionally described as running in parallel to the muscles. Their function is to provide support to the joint at the ends of its range of motion (figure 1.2).
Ligaments are traditionally described as (a) running in parallel to the muscles and (b) functioning primarily when under tension at the end of a joint’s range of motion. Reprinted, by permission, from J. Van der Wal, 2009, "The architecture of the connective tissue in the musculoskeletal system - an often overlooked functional parameter as to proprioception in the locomotor apparatus," International Journal of Therapeutic Massage & Bodywork 2(4): 9.23.
As our understanding of the role of fascia throughout the body has deepened in recent years, many of our classic explanations are being challenged. Dutch osteopath and anatomist Jaap van der Wal has published a research paper that looks at the body from an architectural perspective rather than the typical anatomical dissection perspective (2009). He describes ligaments, based on his observations during careful dissections, as being continuous with the fascial sleeve in which muscles run; therefore, they are considered to run in series with muscle tissue and not as parallel, but separate, entities. Ligaments appear to provide support to the joint structure throughout the joint’s range of motion. Van der Wal coined the term dynament ("dynamic ligament") to more clearly describe the function of ligaments that form synovial joints (figure 1.3).
(a) Van der Wal coined the term dynament ("dynamic ligament") to describe muscles and ligaments that run in series with each other. (b) The dynament is under tension and provides support in all joint positions. Reprinted, by permission, from J. Van der Wal, 2009, "The architecture of the connective tissue in the musculoskeletal system - an often overlooked functional parameter as to proprioception in the locomotor apparatus," International Journal of Therapeutic Massage & Bodywork 2(4): 9.23.
Even as our understanding of the structure and function of ligaments broadens to include this architectural viewpoint of the transmission of forces across joints, we must still be cautious with stretching. Ligamentous tissue has a different ratio of collagen to elastic fibers than does tendinous tissue. Ligaments provide the majority of resistance to movement at the end range of a joint. If they are repeatedly overstretched, they lose their ability to return to their normal length and to stabilize the joint. This creates joint laxity and sets the stage for joint injury.