240 Dance Anatomy and Kinesiology
1996). Instead, key ligaments are taut to favor stability
when the knee is extended, while key ligaments are
slack to favor mobility when the knee is flexed.
Four knee ligaments that are particularly impor-
tant are the paired collateral ligaments and the
paired cruciate ligaments. As seen in figure 5.3, the
collateral ligaments run longitudinally on each side
of the knee, while the paired cruciate ligaments are
located within the knee joint.Medial Collateral Ligament
(Tibial Collateral Ligament)
The collateral (side by side) ligament located on
the inside of the knee joint is called the medial col-
lateral ligament (MCL) or tibial collateral ligament
(see figure 5.3). This ligament is composed of two
layers, a superficial and a deep layer (Magee, 1997).
The superficial layer is a broad, flat, membranous
band that joins the medial condyles of the femur and
tibia. The deep layer of this ligament runs inferiorly
from its proximal attachment on the medial condyle
of the femur and merges with the joint capsule and
with the capsular fibers that attach the margins of
the medial meniscus to the edge of the tibial condyle(coronary ligaments). Although the medial collateral
ligament is stronger than its lateral counterpart
(the lateral collateral ligament), it is much more
frequently injured.
The medial collateral ligament becomes taut
with knee extension and external rotation. It is key
for medial stability of the knee and is the principal
restraint to forces that tend to open up the inside of
the knee, termed valgus stress (L. valgus, turned out-
ward). At 25° to 30° of knee flexion, almost 80% of the
valgus stress to the knee is supported by the medial
collateral ligament (Besier, Lloyd, Cochrane, and
Ackland, 2001). This valgus type of stress can occur in
dance when the knee is allowed to fall inward relative
to the foot, for example in a poorly performed plié.
The medial collateral ligament also is a key restraint
for external rotation of the tibia whether the knee
is flexed or extended (Levangie and Norkin, 2001).
This may contribute to the vulnerability of the medial
collateral ligament to injury in dancers.Lateral Collateral Ligament
(Fibular Collateral Ligament)
The collateral ligament located on the outside of
the knee joint is called the lateral collateral liga-FIGURE 5.2 Movements of the knee joint. (A) Open kine-
matic chain flexion-extension, (B) closed kinematic chain
flexion-extension, (C) external rotation-internal rotation.FIGURE 5.3 Key knee ligaments and the menisci (right
knee, anterior view).