by Baxter
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| Knee Joint (with ligaments) |
Let’s begin by looking at some basic definitions for these two structures. Both ligaments and tendons are composed of something anatomists call “connective tissue,” which is a collection of tissue types that often serve the function of keeping our different body structures together, and include such diverse tissues as the above tendons and ligaments, as well as fascia, intervertebral discs, cartilage in the ears and nose, cartilage coating the ends of bones and others. Connective tissues, depending on what their function in the body is, will either be more or less elastic by virtue of the proportions of the components that make up connective tissue: collagen and/or elastin fibers, which float in a semi-fluid gel called ground substance. According to Mel Robin, in his book A Physiological Handbook for Teachers of Yogasana, connective tissue works as a mechanical support or binder for other tissues, allows for food and waste from cells to move in and out, acts as a lubricant and is the body’s glue.
So what then are the structures that ligaments glue together and what are the unique features of ligaments? Ligaments are specialized connective tissue that binds bones to bones. They keep the bones of your joints in close proximity so they don’t dislocate (which sometimes still can happen, in the shoulder joints, for example), and they allow for a certain amount of passive movement in some directions and restrict movement in others. In fact, restraining movement is one of the main functions of ligaments. They happen to be high in collagen fibers and low in elastin fibers, which makes ligaments strong, but not very flexible. According to David Coulter in his book Anatomy of Hatha Yoga ligaments are:
“...made up of tough, ropey, densely packed inelastic connective tissue fibers, with only a few cells interspersed between large packets of fibers.”
Usually, the amount of stretch that can take place in a ligament is very minor, only around 4%, but there are exceptions, such as ligaments in the cervical spine region, which have been found to stretch up to 200%! In contrast, those around the knee joint have very little elastin, so are much more rigid to provide more stability to the joint. This can have relevance for our yoga practice. As an example, deep flexion (forward bending) of the neck as in Shoulderstand will not permanently overstretch the neck ligaments. But deep flexion (bending) of the knee as in Supta Virasana has to be approached cautiously and mindfully so as to not overstretch the supporting ligaments of the knee. If the ligaments are overstretched, they will not return to their original length and will be permanently loose and ineffective in stabilizing the knee. In general, you want to focus on stretching the muscle and not the ligaments in your yoga practice.
Another reason to avoid overstretching or, even worse, tearing a ligament, is that ligaments have a poor blood supply. Due to this poor supply, getting repair cells into an injured ligament and taking away the waste and injured material is more difficult, and healing is therefore slow. Also, ligaments have very few cells—which are the things that have to be stimulated in an injury to produce more fibers and fluid—and this contributes to slow healing as well.
Those out there who have injured the ligaments at the side of the knee joint, the collateral ligaments, via sports like soccer or football, can attest to the long healing times I am referring to here. When we sprain a ligament, not only do we experience some pain and swelling, but the area also seems looser and more prone to re-injury. A ligament sprain that almost everyone has experienced at one time or another like this is the outer ankle.
It seems that one of the safest ways to stretch your tight muscles, and avoid stretching your supportive yet rigid ligaments, is via moderate intensity, slow, held stretches. Warmer muscles and ligaments seem to do this more healthily then cold ones, so I like to move slowly and mindfully in and out of a position a few times to warm up the tissues, and then follow that up with a more sustained hold. And the good news regarding safe stretching is that our nervous system warns us as we approach the kind of overstretch that could tear our ligaments (and tendons) through pain (which can have a whole range of variety and intensity), trembling or weakness. This is yet another reason to pay close attention to the sensations that arise as you perform your asanas. Also important is the location of the sensations, as those arising in the mid-length of the muscles is much more acceptable than sensations occurring right over joints. You might hang in there a bit longer in the first instance and come out of a stretch promptly in the latter!
Next time, I’ll discuss tendons, which share some similarities with ligaments, but have some unique functions as well.
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