These are two of the most important joints for
the yogi to understand, for they are central to a safe,
comfortable and ever-deeper practice of the asanas.
The knee joint is the largest, most
complicated joint in the body. It's also integral to and often
vulnerable in many asanas. Therefore yogis need to understand
the knee's structure in order to avoid knee injuries.
Particularly risky are poses in which the knee is flexed yet
carries weight, and sitting poses such as
siddhasana.
Three bones meet at the
knee:
the femur (thigh), tibia (shin)
and fibula. Cartilage is attached to the end of each of these
bones. In addition, between the femur and tibia are the
medial meniscus and lateral meniscus, which are two
semicircular pieces of cartilage (semilunar cartilage)
that serve as shock absorbers. In the middle of the joint
are the two cruciate ("crossed") ligaments, which
prevent forward and backward slippage. Around the whole joint
is a tough fibrous covering called the
capsule.
The knee is a hinge joint; it is
designed not to bend sideways or backward
(hyperextension), except to very small degrees. This is why,
although it's often recommended that one contract the
quadriceps in forward-bending asanas (to stabilize the knee as
well as to release the hamstrings via reciprocal inhibition),
that may not be advisable for persons who have a tendency to
hyperextend the knee. Be sure that all rotation (when bending
the knee) takes place in the hip joint, because it is possible
to rotate the knee slightly in effect, bending it sideways
which can damage ligaments and/or cartilage. Most easily
damaged is the meniscus, because it is fairly easy to catch
this cartilage between the two bones and tear it. Torn
cartilage can result in great pain, and it will need to be
surgically removed. Helping guard against sideways bending are
the collateral (side) ligaments medial and lateral which are
on either side of the joint capsule. These ligaments are aided
in this task by the ends of the hamstring muscles, which wind
around the sides of the knee. This is not a "fail-safe"
mechanism, however, because the collateral ligaments and
cruciate ligaments can also be torn by twisting the knee. In
the realm of athletics/ the terms "torn meniscus" and "torn
anterior cruciate ligament" are all too familiar and
dreaded.
Knee Cautions
To summarize the knee cautions for asana
practice (and any other movement or position):
• Don't hyperextend, 'Lock" the
.knee.
• Don't twist, rotate, torque the knee. When a
leg is supporting weight, keep the knee pointing in same line
as toes. When entering a cross-legged position, let all
rotation come from the hip joint.
• Don't extend knee beyond ankle when leg is
bent and bearing weight (e.g., virabhadrasana,
lunges).
• Don't move the knee medially or laterally
when the foot is in a fixed position.
• Be careful (especially with
weak or injured knees) when knees are in extreme flexion with
leverage being applied (e.g., balasana, supta
vajrasana).
