The Knee and Patellofemoral Joints 265and active insufficiency delayed. Consciously using
this principle when performing this movement—that
is, concentrating on fully hyperextending the hip
and feeling the rectus femoris stretch across the
hip and the hip extensors (hamstrings) lift the knee
up, before extending the knee—can often help you
maintain a greater height of the leg as the knee is
extended.
Lombard’s Paradox
As discussed in chapter 2, in accordance with
Lombard’s paradox, when the hamstrings and rectus
femoris simultaneously contract, extension of both
the knee and hip will tend to predominate (Lom-
bard and Abbott, 1907). This co-contraction of the
quadriceps and hamstrings to produce knee and
hip extension is frequently used during everyday as
well as dance movements, as in standing up from a
chair, the up-phase of pliés, and the takeoff phase
of jumps.
Special Considerations for the Knee in Dance.
When taking into account the mechanics of the tib-
iofemoral and patellofemoral joint, there are several
issues in dance that warrant further discussion. These
issues include use of the grand plié, twisting of the
knee in turnout and other movements, knee hyper-
extension, and specific muscle use as they relate to
achieving the desired aesthetic of common types of
dance while keeping knee injury risk low.
The Grand Plié
There is much controversy about the use of a full
squat or grand plié. Concerns cited are the large
stresses applied to the menisci and posterior cruciate
ligament (Escamilla, 2001) and the dislocating force
due to the approximation of the calf and back of the
thigh and the parallel component of the hamstring
muscles (angle of muscle attachment—chapter 2), as
well as very high associated patellofemoral compres-
sion forces. These concerns have led to the common
recommendation of limiting active knee flexion
(such as accompanies squats, pliés, and lunges) to
about 90° or a position in which the thigh is parallel
to the floor (parallel squat) for recreational athletes
or deconditioned older individuals.
However, the application of these recommenda-
tions to competitive athletes, including well-condi-
tioned dancers, is highly debatable. Critics of this
conservative approach hold that a fuller range of
motion is needed to develop adequate strength and
explosive power necessary for high-level athletic
performance. They also hold that such exercises,
if performed with good technique and advanced
appropriately, can actually have a protective effect
through strengthening the knee structures and
involved musculature, such that greater forces can
be withstood during activity before injury occurs.
Looking at this issue as specifically related to
dance, there are several additional factors that
should be taken into account. First, potential risk to
the knee is probably lessened by (1) the traditional
use of music and counts to encourage a slow and
controlled descent and rise from a plié; (2) the com-
monly used directive to “lift out of your knees,” as
well as to avoid hesitating, or “sitting,” at the bottom
of the plié and to instead keep movement continu-
ous; (3) the use in some dance forms of a barre,
which can aid with balance, as well as in some cases
provide some unweighting of the knees; (4) the lack
of external weights (such as barbells) so that only
body weight is of concern; and (5) the common
use of turned-out positions that may recruit other
muscles such as the hip adductors and lessen the
required magnitude of quadriceps contraction and
resultant patellofemoral compression forces. Fur-
thermore, performing pliés in different positions
may represent slightly different benefits and risks.
For example, third- and fourth-position grand pliés
performed center floor not only require marked
strength in the quadriceps but also high skill levels to
maintain balance, turnout, and alignment and have
been found to involve greater overall longitudinal
rotation at the knee relative to second-position grand
pliés (Barnes et al., 2000).
Lastly, potential functional strength benefits
should be considered. Many female dancers have
lower absolute quadriceps strength levels than some
other types of athletes or than might be desired
(Kirkendall et al., 1984; Koutedakis, Agrawal, and
Sharp, 1998; Koutedakis et al., 1997; Mostardi et al.,
1983), and grand pliés (as well as jumps and hinges)
are among only a few exercises that include sufficient
overload to effectively enhance strength. Not to
provide adequate stimulus to improve quadriceps
strength and not to allow practice of motor patterns
including marked knee flexion in a slower, more
controlled manner might actually be a disservice to
dancers and increase their risk when choreography
demands the use of full knee flexion, often at a faster
tempo and in a more complex movement pattern
later in the class or in rehearsal and performance
(figure 5.22).