Your instructions in standing poses can help save your students a lot of pain, both now and decades from now. The culprit is osteoarthritis, the "wear-and-tear" arthritis, of the knees. Good weight-bearing alignment, learned and practiced in yoga class, can help keep the knees happy and healthy. On the other hand, bad alignment in poses—heaven forbid—can actually contribute to the breakdown of the joint surfaces, and the subsequent painful inflammation, caused by osteoarthritis.
There's a lot of talk about arthritis these days (or is it just that we're all getting older?), so let's start by examining its nature. Breaking down the word, "arth-" means joint, and "-itis" means inflammation. Most of the joints in the body, except the spinal discs, the S.I. joints, and a few others, are synovial joints. Synovial joints are freely moveable and filled with slippery synovial fluid, while the ends of the bones are covered with smooth, whitish hyaline cartilage where the bones come together. With time, injury, or joint misalignment, this cartilage can wear down, which causes roughened joint surfaces. The chips and "dust" of cartilage floating in the synovial fluid irritates the synovial membrane lining the joint capsule, and it produces the pain and swelling associated with this problem. Osteoarthritis gradually limits the joint's range of motion, and it can be mild, moderate, severe, or eventually bone-on-bone, which is incredibly painful.
Why Yoga Helps
Now, how is yoga going to affect this process? Osteoarthritis occurs at the point on the joint surface that bears the most weight during repeated movements over long periods of time (although injury can also initiate the process). Many people have unhealthy knee movement patterns when they come to yoga, which causes excessive wear on one specific area of the joint surface. They'll continue using these patterns in their standing poses unless they learn otherwise. This means that we, as yoga teachers, have the opportunity to teach healthy knee alignment and movement patterns to our students as they learn the poses.
The weight-bearing part of the knee joint is formed between the top of the tibia (shinbone) and the bottom of the femur (thighbone). That end of the femur forms two large knobs, the condyles, which are smooth and covered with hyaline cartilage. There are matching indentations on the top of the tibia, also covered with hyaline cartilage. These two matched sets form the medial and lateral compartments of the knee joint. Ideally, your body weight should be balanced between these two compartments, so that neither side bears substantially more weight than the other.
Additionally, while bearing weight, the knee should move only in flexion and extension (bending and straightening), without twisting or bending to the side. To imagine twisting on a weight-bearing knee, put the heel of one hand in the palm of the other, with your fingers lined up. Then rotate your hands so the fingers of one hand are no longer aligned with the fingers of the other hand. Did you feel the friction between the palm and the heel of the hands? That's similar to the torsion forces on the cartilage surfaces of the tibia and femur, which can contribute to wear and tear. When the knee is bent and not bearing any weight, the knee can actually rotate moderately, without the destructive combination of torsion and pressure.
To understand sidebending at the knee, picture bowlegs. Bowlegs put significantly increased pressure on the medial compartment cartilage, and they overstretch the ligaments and other soft tissue on the outer knee. Conversely, knock-knees (the opposite problem) put increased pressure on the lateral compartment cartilage and strain the soft tissue of the medial, or inner, knee. This problem is more common in our society, and is associated, as you might expect, with arthritis in the lateral compartment.
Teaching Correct Knee Poses
When you teach your students to align the kneecap with the center of the foot, you're actually training them to avoid rotation of the knee. The usual "bad" habit involves the kneecap, which indicates the position of the femur, turning in while the foot, which generally indicates the position of tibia, turns out. It takes a firm contraction of the buttock muscles-including the gluteus maximus but especially the piriformis and the other five deep hip rotators-to externally rotate the femur against the tight inner thigh muscles. If these muscles, primarily the adductors, are especially tight, your students may need extra work to stretch them in such poses as Supta Padangusthasana (Reclining Big Toe Pose) and Utthita Hasta Padangusthasana (Extended Hand-to-Big-Toe Pose), with the leg opened out to the side in both.
If your students take the same common (but incorrect) knee alignment into bent-knee standing poses, such as Virabhadrasana I and II (Warrior Pose I and II), the knee is again rotating but also bending to the side. Again, strong external rotators are required to pull the femur into line. A good way to practice the proper alignment is to set the pose up with your student's back to the wall, right buttock on the wall, right foot turned out, and left foot turned in. Getting ready for Virabhadrasana II, notice that, in order to align the kneecap and the foot, the left pelvis needs to move a little bit away from the wall (the pelvis will not be parallel to the wall—also true in Trikonasana, or Triangle Pose). As the right knee bends, the femur should stay parallel to the wall, keeping the back knee straight as the student presses out into the left foot.
It's even more challenging to keep healthy knee alignment during transitions from bent-knee to straight-knee standing poses, such as Trikonasana to Ardha Chandrasana (Half Moon Pose) and Virabhadrasana I to III. It's difficult for most students to keep the knee from turning in, and even experienced students may need to work with support, such as having their backs to the wall for Trikonasana to Ardha Chandrasana. Students can practice bending and straightening the standing knee in Virabhadrasana III with their hands on a ledge or wall, while keeping the lifted leg straight and strong. In both cases, students usually need to look at their front knees in the beginning, to confirm that they're holding the alignment during the transition.
As you remind your students to be mindful of knee alignment in standing poses, you'd be performing an invaluable service if you also tell them to keep the same alignment in their activities off the mat. If they practice the movement they've learned in class while ascending and descending stairs, getting up and down from chairs, and any time they need to step up or down, not only will they be avoiding the pain and limitation of arthritis, but they'll be practicing yogic awareness all day long.
Julie Gudmestad is a certified Iyengar Yoga teacher and licensed physical therapist who runs a combined yoga studio and physical therapy practice in Portland, Oregon. She enjoys integrating her Western medical knowledge with the healing powers of yoga to help make the wisdom of yoga accessible to all.