Do Ligaments Contract?

The following information is just that…information and nothing more. I do not influence you to believe one way or the other, although looking at our current understanding of the body, I think that we walk away asking more questions and still looking for answers.

First I want to thank the Facebook community of manual therapists of all kinds for all the amazing positive support and the continual encouragement I have received encouraging me to continue to provide updated and important research information concerning the involvement of ligamentous tissues in patients recoveries and treatments.

I receive some of the most in depth questions/comments concerning ligament/joint recovery and treatment. In order to answer many of these questions, I find myself most commonly either demystifying old beliefs and trends or educating on the current and important research demonstrating the importance of understanding the role that ligamentous tissues play in our patients rehabilitative programs.

Unfortunately there is still much miss information and much misunderstanding about the role of ligaments in injuries and how they heal…if they ever heal. For example did you know that in injuries where chronic inflammation has been allowed to persist, the ligamentous tissues would never recover! NEVER! This is documented research! So much for the myth, currently still being taught everywhere, that sprains are completely healed in approximately 90 days.

This is an amazing time to be a manual therapist. I have never seen a time where we are more research informed. Because of the lack of research into the various specific treatment modalities, the effect of almost every technique we perform on our patients is theory, assumption and suspect. Everything is up for question.

We also have to remember and accept that the human organism is the most advanced machine on the planet. It has been shown to be able to perform and perceive in ways that science currently cannot explain.

One of the most common questions I receive is: Do ligaments contract like muscles?

The short answer is I don’t think so, but recent Fascial research shows that there is possibly the potential for it.

First lets review the current understanding of the structure of ligaments.
There seems to be quite a bit of old myths, trends in beliefs, and miss information about the mechanical properties of ligaments.

Ligaments consist of closely packed, parallel collagen fibers which appear to have various degrees of undulation (or helical) form along the axis of each fiber at a resting length. There are also short cross fibrils, which connect the axial fibers to each other. The helical shape of various wave size of each fiber or group of fibers (bundles) gives rise to a process called ‘‘recruitment’’. As axial stretching of a ligament is applied, fibers or bundles with a small helical wave appearance straighten first and begin to offer resistance (increase stiffness) to stretch. As the ligament is further elongated, fibers or fiber bundles of progressively larger helical wave straighten and contribute to the overall stiffness. Once all the fibers are straightened a sharp increase in stiffness is observed. Over all, the recruitment process gives rise to a non-linear length–tension relationship of a ligament.

Overall, the mostly collagen (75%), elastin and other substances structure of ligaments is custom tailored by long evolutionary processes to provide various degrees of stiffness at various loads and at various ranges of motion of a joint, while optimally fitting the anatomy inside (inter-capsular) or outside (extra-capsular) a given joint. The various degrees of helical shape of the different fibers allows generation of a wide range of tensile forces by the fiber recruitment process, whereas the overall geometry of the ligament allows selective recruitment of bundles such as to extend function over a wide range of motion. The large content of water (70%) and the cross weave of the long fibers by short fibers provides the necessary lubrication for bundles to slide relative to each other, yet to remain bundled together and generate stiffness in the transverse directions.

Ligaments have mechanical properties known as creep, tension/relaxation, hysteresis and strain.
The collagen fibers of the ligaments were shown to be viscoelastic and the fibers were shown to be at various levels of laxity or tension such that elongation created a process of recruitment, which increased with length allowing increase in tension.

The various lengths of time and forces applied to these structures have been shown to cause either a temporary or permanent change to their structure. When a constant load is applied to a ligament, it first elongates to a given length. If left at the same constant load, it will continue to elongate over time in an exponential fashion up to a finite maximum. This elongation over time is termed ‘‘creep’

Another important behavioural property of ligaments is its inability to track the same length–tension curve when subjected to a single stretch–release or load–unload cycle, i.e. hysteresis. This phenomenon is also associated with repetitive motion when a series of stretch–release cycles are performed over time such as a CTD (cumulative trauma disorder.)

The impact of hysteresis, therefore, is manifested by gradually decreasing tension in the ligament, development of joint laxity, reduced joint stability and increased risk of injury. It is evident, therefore, that loading or stretching a ligament over relatively short periods, induces changes in its length–tension behavior that may last 20–40 times longer than the duration of the loading/stretching

The interaction of’ several ligaments associated with the same joint provided joint stability for most of the range of motion in several axis, allowed equal pressure distribution of the two cartilage surfaces and keep the surfaces moving on a prescribed track. Such data confirmed the mechanical properties of ligaments as joint stabilizers.

Ligaments can feel taught when placed under tension. This can be accomplished through equal traction/distraction of a joint or asymmetrically be placing the joint into a position where one side of the joint is approximated while the other side is distracted. The ligamentous tissue on the side of where the approximation is will feel slackened, while on the side of the joint that has been gapped the ligamentous tissues tighten.

I think that there is a possibility for the manual therapist to hallucinate a contracted ligament when it’s most likely this situation.

Ligamento-muscular reflex
Clear evidence has been provided to explain the function of the ligamento-muscular reflex as a synergistic sensory motor control scheme for maintaining joint stability,

decreasing and/or preventing risk of damage to the ligament via co-activation. Co-contraction allows for a measure of joint stability throughout normal motion, the triggering of the ligamento-muscular reflex can provide a fast dose of increase in joint stability when unexpected movement occurs, eliciting sudden increase in ligament tension. It is a protective reflex proving the synergistic relationships of ligaments and muscles in maintaining that stability.

The ligamento-muscular reflex is much more complex than a hard-wired neurological process which triggers or suppresses muscles responses upon stretch of the ligaments. The reflex is governed by a complex neural network taking into account joint stability, internal mass and its implication in light of movement velocity and acceleration, orientation to gravity. etc. It is not a simple reflex by any stretch of the imagination. This reflex is a fact. Researchers have found it in mice, rats, dogs, cats and humans.

So, ligaments have either an inhibitory or excitatory effect on muscles, but does it work the other way round? Again, more questions than answers.

Fascial Research: Myofibroblasts and Fascial Tonus Regulation
Myofibroblasts are connective tissue cells that contain dense stress-fiber bundles composed mostly of alpha smooth muscle actin. First discovered by a group working under Gabbiano and Majono (see Montandon et al.) in the early 70’s, the myofibroblasts have also been shown to play a major role in wound healing and also to be involved in many other normal and pathologic con- tractile tissue processes. Most of these cells develop out of normal fibroblasts stimulated by the influence of mechanical tension and specific cytokines. A smooth mus- cle–like contractility enables these cells to maintain contractile force over long durations with little energetic cost. An increased presence of myofibroblasts is a driving factor behind chronic fascial contractures such as those in Morbus Dupuytren, plantar fibromatosis, excessive scar formation, and frozen shoulder. Recently, the presence of myofibroblasts (or myofibroblast-like contractile cells) has also been demonstrated for normal dense connective tissues such as joint ligaments, menisci, tendons, organ capsules, and others.

Langvein suggests that connective tissue may transmit electrical, cellular, and tissue-remodeling signals throughout the body, each in response to mechanical forces, but on different time scales. Many tissues, including collagen, display immediate local electrical gradients in response to mechanical stress. Mechanical contacts between fibroblast cells are actively altered within minutes. Finally, tissue remodeling has been shown in tendons, ligaments, and joint capsules, and if this process is also present in loose connective tissue, it would provide a body-wide pattern for remodeling connective tissue based on movement and local tissue stress. Interactions among these three systems could provide both short-term and long-term responses.

In 2009, Jaap van der Wal research states that there is one joint stability system, in which muscular tissue and RDCT (regular dense (collagenous) connective tissue) interweave and function mainly in an “in series” situation rather than an “in parallel” situation. Thus, in vivo, the periarticular connective tissue is loaded and stretched both by the movement of related skeletal parts and by the tension of the muscle tissue inserting to this connective tissue. Ligaments are considered RDCT’s.

Most deep and superficial RDCT layers (as muscle compartment walls) are organized in series with muscle fascicles. Collagenous fibers running from bone to bone—thought to be stressed passively by displacement of the articulating bones—hardly occur. Instead, there occur broad aponeurotic layers of RDCT to which relatively short muscle fascicles insert, which, on the opposite side, are directly attached to skeletal elements. Such configurations of muscle fascicles attached to the periosteum of one articulating bone and via a layer of RDCT indirectly attached to another articulating bone, could be considered “dynamic ligaments.” Such “dynaments” are not necessarily situated directly beside the joint cavity or in the deep part of the joint region.

By describing the dynament as an architectural unit of the musculoskeletal system, we mean a unit of RDCT connected to the periosteum of a skeletal element with muscle fascicles in series attached to it.

So… What do you think?
Are we hallucinating a contracted ligament when it possibly is just the ability to differentiate that on one side the tissue is taught and on the other it is slackened?

Is the Ligamento-muscular reflex and/or the contractile ability of Fascial tissues, of which Ligaments are part of, strong enough for us to feel and are we able to create a therapeutic environment that allows us the opportunity to take advantage of it in a positive fashion?

Dynaments! I like the “in series” description of interacting tissues working as a unit. Does this situation provide the best scenario for the possibility of a ligament to contract… or to feel contracted as the surrounding musculature contracts?

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