Preventing Yoga Injuries vs Preventing Yoga: The Hip Labrum
I’m thinking the ancients were onto something. Meaning this (possibly) 5,000 year old art that so many of us enjoy practicing and teaching. I’m talking about the tradition of Hatha yoga. The one that includes putting our bodies into poses like Uttanasana, Dandasana, Padmasana (Full Lotus), Sirsasana (Headstand) etc. Now, part of that practice involves poses that take some of our joints to the extremes of their range of motion (from a western medical perspective). Indeed, many of the benefits of Hatha yoga derive from moving our joints (carefully) within their range of motion.
Obviously, we want to avoid injuries when practicing yoga. One way to do that is to eliminate a bunch of the asanas on the grounds that they’re “too dangerous”. That approach also eliminates the benefits of those poses. Or, we can practice mindfully, using modifications where appropriate and working in a progressive manner towards the classical asanas that are appropriate for each of us individually. Knowledge of the body combined with awareness of mechanisms of injury aids in this process.
In medicine, we look for ways to eliminate the risks of a given activity, not the activity itself. To illustrate my point, check out this quote from one of the scientific articles that studied the effect of extreme hip motion in professional ballerinas:
“These results do not mean that the dancers should stop executing these movements, but rather they should limit them in frequency during dancing class.”
Wow. Think I’m down with that.
You mean we don’t have to toss out Developpe Devant, Developpe a la Seconde, Grand Ecart Facial and Grand Ecart Latéral and create a new “gentler ballet”? Of course not. Because it would be kind of boring to watch a ballet that consisted of folks sitting on a stage, waving their arms around (to say nothing of the dangers to the rotator cuff). Similarly, Hatha yoga wouldn’t have its beneficial effects without, you know, the poses of Hatha yoga.
So, with this in mind, let’s review the structure of the hip, paying particular attention to the labrum.
As a general consideration, mobility and stability of the joints are determined by three factors. First, there is the shape of the bone at the joint; for example a ball and socket vs a hinge. Next there are the soft tissue stabilizers such as the ligaments, capsule, labrum or meniscus. Finally, there are the muscular stabilizers that surround a given articulation. A related subject is the concept of joint congruency. This refers the fit of opposing joint surfaces. High joint congruence means there is more surface area in contact; low joint congruence decreases the contact area.
A central tenet of rehabilitation and injury prevention relates to strengthening the muscular stabilizers of the joints. This aids to enhance congruency of the articular surfaces while at the same time providing dynamic support for the soft tissue stabilizers such as the ligaments, labrum and menisci. For example, in sports that put the soft tissue and bones at risk, we integrate training that improves proprioception and strengthens the muscles surrounding the joints.
Let’s begin by looking at the acetabular labrum. This is a fibrocartilaginous ring-like structure that encircles the outer edge of the socket of the hip joint. Like the meniscus of the knee and the labrum of the shoulder, the hip labrum deepens the joint and contributes to its stability, while aiding in pressure distribution along the articular cartilage. It also acts as a type of seal that helps to retain the synovial fluid within the joint itself, thus allowing for some of the load on the joint to be borne by fluid pressurization, while at the same time helping with joint lubrication.
The labrum is relatively avascular, with blood vessels entering near the peripheral edge where it attaches to the bone and cartilage, and penetrating about one third of the way into the structure. This limits its ability to heal. Tears of the labrum are associated with hip osteoarthritis. Figures 1 and 2 illustrate the hip labrum from the outside of the joint and the acetabulum with the femur removed.
The hip is a synovial joint. These types of joints are surrounded by a capsule, which is lined by a synovial membrane (synovium) which faces the joint cavity. The synovium contains two primary cell types. The first are called fibroblasts and they secrete synovial fluid. This fluid lubricates the joint surfaces, reduces friction during movement and acts as a shock absorber through fluid pressurization. It also carries oxygen and nutrients to the articular cartilage and removes carbon dioxide. The other cell type lining the synovium is a macrophage cell; this cell removes debris or other unwanted material from the joint space. Activities that maintain joint range of motion aid in circulating the synovial fluid and bringing unwanted material into contact with the macrophages. Figure 3 (above) illustrates the joint capsule with the synovium for the hip.
On the outside surface of the hip capsule are the ligaments. The iliofemoral ligament runs from the anterior inferior iliac spine (AIIS) to the front and lateral part of the top of the greater trochanter of the femur. The iliofemoral ligament is the strongest ligament in the body. It functions to resist extension and external rotation of the hip and helps to prevent the pelvis from tilting backwards during standing. It also stabilizes the pelvis during the stance phase of walking, thus assisting the hip abductors. The pubofemoral ligament runs from the pubis to the neck of the femur; it prevents hyperextension and hyperabduction of the hip. The ischiofemoral ligament runs from the ischium in a spiral manner to the femoral neck. This ligament tightens in hip extension and becomes loose during flexion. The image above illustrates the hip ligaments.
Finally, there are the muscular stabilizers of the hip. I’m not going to discuss the specific actions of the individual muscles in this post. What I want to illustrate is the positions of the muscles around the joint. For example, look at the psoas and the rectus femoris muscles and how they provide an anterior support to the hip. The images below illustrate the muscular stabilizers of the hip joint.
1-iliopsoas, 2-pectineus, 3-rectus femoris, 4-sartorius, 5-gluteus medius,6-tensor fascia lata, 7-piriformis, 8-external rotators, 9-quadratus femoris
Take your time going over this material, and use the great images Chris produced to help you understand the hip joint. Stay tuned for Part II of the series, where we’ll go over some of the latest scientific research being conducted on the hip joint (research for which all of us in yoga should be extremely grateful, btw).
As always, if you have pain in your hips (from any activity), be sure to consult a health care professional who is trained and qualified to diagnose and treat such conditions.
Ray and Chris