Dance Anatomy & Kinesiology

248 Dance Anatomy and Kinesiology

Palpation: Stand on your left leg with the ball of your right foot about 10 inches (25 centimeters)

behind the left foot and the right knee bent. In this position the biceps femoris can be palpated on the

right leg along the lateral posterior thigh, with the tendon easily palpated immediately proximal to the

back of the knee. The semitendinosus tendon can also be palpated immediately proximal to the back

of the knee, only on the medial side of the posterior thigh. The semimembranosus can be palpated

on either side of the semitendinosus tendon. Flexing the knee by lifting the foot off the floor, with your

hand placed just above the knee joint (posteriorly), allows you to feel the hamstrings contracting and

makes the tendons more prominent.

Popliteus

The popliteus is a small muscle running behind the knee, as shown in figure 5.7B, that is key for knee

joint stability and proper mechanics. It is the most deeply located muscle in this region, lying close

to the knee joint capsule. It attaches proximally to the lateral femoral condyle, lateral meniscus, and

fibula, and distally to the posteromedial aspect of the tibia. When the tibia is fixed such as during

weight bearing, the popliteus (L. poples, ham/posterior knee) acts to externally rotate the femur and

also withdraws the lateral meniscus at the beginning of knee flexion. When the knee is straight, this

external rotation function is important to unlock the knee and allow flexion to proceed. In open versus

closed kinematic chain conditions when the tibia is free, such as when one performs a circling motion

of the foot in the air (rond de jambe en l’air), the femur acts as the fixed segment and the popliteus

acts on the tibia versus the femur, producing internal rotation of the tibia.

Palpation: Because of its deep location and because it is covered by the plantaris and lateral head

of the gastrocnemius, the popliteus cannot be readily palpated.

Gastrocnemius and Plantaris

The gastrocnemius and plantaris are more fully described in chapter 6 with the ankle and foot (figure

6.15, p. 313). The plantaris (L. relating to the sole of the foot) can act as a weak assistant to knee

flexion. The gastrocnemius (G. gaster, belly + kneme, leg) originates above the femoral condyles and

inserts into the calcaneus via the Achilles tendon. In non-weight-bearing positions, such as a back

attitude, the gastrocnemius may assist with knee flexion. However, when the foot is fixed and the knee

is in strong extension, such as when functioning as the support leg during movements at the barre or

center floor, the gastrocnemius may reverse its role and pull down and back on the femoral condyles

and help maintain knee extension versus producing knee flexion.

Additional Secondary Muscles of the Knee

The sartorius and gracilis are biarticular muscles whose primary function at the hip was discussed

in chapter 4, but they also cross and can act on the knee joint. They insert on the medial aspect of

the proximal tibia in combination with the semitendinosus. The tendinous expansions of these three

muscles where they attach onto the medial tibia are referred to as the pes anserinus (L. pes, foot +

anser, goose) as seen in figure 5.8. The sartorius and gracilis aid the medial hamstrings with knee flexion

Attachments and Primary Actions of the Popliteus

Muscle Proximal attachment(s) Distal attachment(s) Primary action(s)

Popliteus

(pop-LIT-ee-us)

Tripartite tendon:

1. Lateral femoral condyle


2. Head of fibula


3. Posterior aspect of lateral
   meniscus

Medial posterior aspect

of upper tibia

External rotation of femur (when

foot fixed)

Internal rotation of tibia (when

foot free)

“Unlocking” knee