Twisting At The Knees

Until now, our discussion of the knee joints has focused on their actions ; hinge joints that permit flexion and extension. In chapter 5, we saw th; t extension places the ligaments of the knee under tension and holds < | components of the joint together, and we saw that flexion permits t! e ligaments to become lax. In this chapter we'll explore the one moveme t not yet mentioned—rotation of the flexed knees.

If you are sitting in a chair with the thighs fixed and parallel to the fl< r, and with the legs perpendicular to the floor, you will be flexing the kn >s 90°. If you have good flexibility, you can rotate your feet out laterally fr m this position about 40°, and you can rotate them medially about 30'. You e the movements of the foot, but almost all of the rotation is happenin} at the knees. If you try the same experiment sitting on a high bench with he knees flexed at a 30' rather than a 90° angle, you'll notice that the amo nt of knee rotation is diminished to about 30° of lateral rotation and about <0° of medial rotation. And of course, if you return to a standing position nd extend the knees, rotation is stopped completely. To make these con ir-isons fairly, of course, you have to keep the thighs stabilized or you wil I dd hip rotation to knee rotation and confuse the two.

Figure 7.5. This twist which started with the thighs addutted and the feet parallel, reveals almost 90° of rotation of the pelvis relative to the feet. This is unusual; most people cannot swivel Iheir hips much beyond 45° with their thighs abducted and feet parallel.

Figure 7.5. This twist which started with the thighs addutted and the feet parallel, reveals almost 90° of rotation of the pelvis relative to the feet. This is unusual; most people cannot swivel Iheir hips much beyond 45° with their thighs abducted and feet parallel.

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The muscles that rotate the flexed knees are the hamstrings (figs. 3.10b, 7.6, 8.9-10, and 8.12) and a small muscle on the back of the knee joint, the popliteus. Two of the hamstrings, the setnitendinosus and semimembranosus muscles, insert on the medial side of the tibia, and are thus medial rotators of the flexed knee; the biceps femoris inserts laterally on the head of the fibula, and is thus a lateral rotator of the flexed knee. To experience this sit upright with your knees flexed 90°. Then grasp the tendons of the semimembranosus and semitendinosus muscles on the medial side of the knee joint, rotate the knee medially as strongly as possible, and feel the tendons get tighter. You can do the same thing with the biceps femoris if you rotate the leg laterally as strongly as possible.

The popliteus muscle is visible posteriorly (figs. 5.24, 7.6, and 8.14); it takes origin from the lateral surface of the femur, runs inferiorly and medially, and inserts on the lateral surface of the tibia. Its anatomical disposition therefore allows it to do double duty as a medial rotator of the tibia and a lateral rotator of the femur. The former is what you notice when you rotate your feet in while you are sitting on a chair, and the latter is what you notice when the muscle torques the thigh laterally from a fixed foot position. This is the more common situation in sports because you frequently rotate the thigh (and with the thigh the rest of the body) with one foot planted on the ground, as when you recover from serving a tennis ball.

Because the knee joints are among the few that permit flexion and extension as well as twisting, and because they are vulnerable to injury when they are flexed, everyone should use caution in approaching hatha yoga postures that involve a combination of flexion at the knees and whole-body twisting. And except for the simplest lunging postures, sun salutations, and squatting on the floor in a symmetrical pose, almost every posture in hatha yoga in which the knees are flexed involves either rotation or torque in the knee joint.

ihe ankles and feet

An astounding number of bones (28) and joints (25) are associated with each foot and ankle (fig. 6.8), and in combination their architecture enables us to support the weight of the body, propel us forward, and accommodate to surface irregularities on the ground. And because most of the basic movements in the foot-ankle complex involve stresses from both torque and rotation, they are included in this chapter.

In chapter 4 we saw how foot position in standing postures affects the joints. With the knees extended, what we referred to as rotating the foot out stretches the medial rotators of the hip, and what we called rotating ®e foot in stretches the lateral rotators of the hip. Later, in chapter 6 we turned 10 the ankles and saw that 30-50" of extension (plantar flexion) takes place

4<>2 anatomy of hatha yoga when we lift up on the balls of the feet, and that 45' of flexion (dorsiflexion 1 needed for pressing the heels to the floor in the down-faring dog.

Twisting (that is, true axial rotation) at the ankle joint is so minim 1 that it is usually not even listed in elementary texts, but careful studi j have shown that those with average flexibility at this site can rotate t semimembranosus sartorius semi-

tendinosus

gastrocnemius muscle: lateral head: medial semimembranosus tendon biceps temoris popllteus muscle

Talis Lateralis

Achilles tendon vastus lateralis biceps temoris semimembranosus tendon

Achilles tendon semimembranosus sc is mi ;le popllteus muscle gastrocnemius muscle: lateral head: medial vastus med talis sartorius semi-

tendinosus cut upper ends of gastrocnr is muscle: medial he. lateral heai bit >s fer iris te¡ on

Figure 7.6. Posterior views of the right foot, ankle, leg, knee joint, and lowe portion of the thigh. A superficial dissection is illustrated on the left, and a deeper dissection (following the removal of the bulk of the two heads of ti gastrocnemius muscle and the hamstrings) is illustrated on the right. When he knee is bent and the thigh is stabilized, the popliteus muscle rotates the le medially, but when the foot is stabilized, the popliteus muscle rotates the 1 'g*1 laterally. In the instance of the right thigh shown above, the popliteus must ± has the effect of rotating the body as a whole around to the right (Sappey)

- THis-rmt; postures 403

foot medially about 70 and laterally about 10C. To experience these rotations, stand with the knees extended and the heels and toes together. Place the hands just above the knees to brace them and hold them together, and tighten all the muscles around the thighs. Then twist to the right keeping the feet flat on the floor. This is critical: the slightest lifting of the heels or the edges of the feet brings other movements into the picture. Under these carefully controlled circumstances you have rotated the right foot medially and the left foot laterally, both at the ankle joints. These axial rotations at the ankles may be minimal, but they are seen in many standing postures, and are therefore an important practical concern.

(Technical note: This is a different use of the word rotation for the feet and ankles than we have used previously. The circumstances just above refer to axial rotation within the ankle joint, not swinging the feet in or out. To keep terminology within reach of lay audiences, "rotation of the feet in and out," or "rotation of the feet medially and laterally," which is the same thing, will always refer to the movements of the feet as a whole unless axial rotation within the ankle joint is specifically indicated.I

To explore rotation of the feet as a whole, stand with the knees extended, the heels together, and the medial borders of the feet at a 90' angle from one another. Under these circumstances each foot will be rotated out (laterally) 45 . Most people can go a little further, perhaps to 70" for each foot (fig. 7.7). Now bring the medial borders of the feet parallel and next to one another. The feet are now rotated to a neutral position. Next, bending the knees as necessaiy, bring the big toes together and spraddle the heels out 90' from one another to rotate the feet in (medially) 4s" (fig. 7.8). And finally, abduct the thighs widely, bend the knees deeply, and try to bring the feet into a straight line. This is a moderately difficult balancing posture in which you have rotated each foot out (laterally) 90' (fig. 7.9).

[Technical note: Always keep in mind that "rotation of the feet," as defined in this book, is to a large extent reflective of rotation of the thighs when the knees are extended, or rotation of the legs when the knees are flexed. Don't get confused: the terminology is logical. If you are looking at and thinking of the thighs, say rotating the thighs. If you are looking at and thinking of the legs, say rotating the legs. And if you are looking at and thinking of the feet, say rotating the feet, even though you are aware that most of that we call rotating of the feet actually reflects rotation of the legs or thighs. Just say what you see, and everyone will know what you are talking ahout: it could hardly be more simple. 1

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