The Knee and Patellofemoral Joints 263FIGURE 5.19 Sample dance movement showing knee flexion and
associated prime movers.
Photo: Roy Blakey. Dancer: Douglas Nielsen in Viola Farber’s “Last Call.”
Knee Extension
Remember that knee extension involves “straighten-
ing” the knee or decreasing the angle of knee flex-
ion. The four quadriceps muscles are the extensors
of the knee and are used concentrically to extend
the knee both when the foot is free and when it is
weight bearing. When the foot is free (open kine-
matic chain), the quadriceps are used to produce
knee extension isometrically in exercises such as
straight leg raises (table 5.3B, p. 275) and concentri-
cally in exercises such as terminal knee extension
(table 5.3C, p. 275) and sitting knee extension (table
5.3D, p. 276). In dance, the knee extensors can be
used concentrically to produce a straight position
of the knee in the gesture leg in the développé
or isometrically to maintain a straight position of
the knee of the gesture leg in the tendu, dégagésFIGURE 5.20 Knee extensors working isometrically to pre-
vent gravity from producing further knee flexion.
Photo: Roy Blakey. Dancer: Douglas Nielsen.(brushes), battements (kicks), and the movement
shown in figure 5.21.
When the foot is weight bearing (closed kinematic
chain), the quadriceps are used concentrically to
extend the knee. This movement is used in walking
up stairs or rising from sitting in a chair. Examples
of strengthening exercises that include this form
of knee extension are the wall squat (table 5.3G,
p. 277) and plié/leg press (table 5.3H, p. 278) and
lunge (table 5.3I, p. 278). In dance, this form of
knee extension is used during rising from a plié
or fondu. Concentric powerful use of the knee
extensors is also operative in movements such as
the takeoff in jumping to help effect the desired
vertical rise of the center of gravity and propel the
body through space as seen on the left leg in figure
5.21. Knee extension is also used isometrically in
dance to maintain an extended knee on the support