Massage & Bodywork

May | June 2014

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Joint Alignment and Rotations of the Knee By Mary Ann Foster The knee is the most frequently injured joint in the body for three reasons: it is the largest, most complex, and most unstable joint. The knee serves as a weight-bearing fulcrum and primary shock absorber between the two longest lever arms in the body—the femur and the tibia. It is made more stable by two large menisci, a substantial joint capsule and network of external strapping and internal cruciate ligaments, and balanced muscular pulls around it. When optimally aligned, these structures work efficiently to absorb shock and minimize wear and tear on cartilage. During movement, multiple compressive and rotational forces exert crushing, grinding, and twisting loads on the knees, particularly on the meniscal disks. To minimize these mechanical stresses, the intricate calibration of each knee requires optimal alignment and precise tracking throughout range of motion. The femoral condyles need to move on the tibial plateau with the precision and balance of a stilt walker. Any slight variance from the optimal pathway of motion can cause repetitive strain and lead to tissue damage. The knees are frequently injured during sports activities, usually from torque or direct impact in contact sports like football (Image 1). Torque injuries tend to occur during quick turns, such as on a racquetball court, when the foot is fixed and the femur twists on the tibia beyond a normal range, tearing soft tissue. People with a knee injury often develop a vaulting gait, rising up on the toes of the unaffected leg to minimize weight on the affected one. FUNCTIONAL ALIGNMENT OF THE KNEE We can measure the functional alignment of the knee by looking at the mechanical axis of the lower limb. In an ideal alignment, the centers of the hip, knee, ankle, and second metatarsophalangeal joint line up along a vertical axis. This alignment should be maintained during motion because mechanical stresses translate from one joint to another. Another measure of knee alignment is the Q angle, which falls along the line of pull of the quadriceps on the knee (Image 2). An average Q angle is 15 degrees, although it can range from 13 to 18 degrees. The Q angle tends to be greater in women because the female pelvis is wider, which increases the oblique angle of the femur. The oblique angle of the shaft of the femur causes a medial displacement of the knee called genu valgum. Five to 10 degrees of genu valgum is normal; a greater degree of displacement results 104 m a s s a g e & b o d y w o r k m a y / j u n e 2 0 1 4 technique THE SCIENCE OF MOVEMENT A common knee injury called the "terrible triad" damages the anterior cruciate ligament, medial meniscus, and medial collateral ligament. 1 Medial collateral ligament Medial meniscus Anterior cruciate ligament 2 Quadriceps line of pull ASIS Q angle Midpoint of patella Tibial tuberosity The Q angle, which falls along the line of pull of the quadriceps, is another measure of knee alignment.

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