Dance Anatomy & Kinesiology

312 Dance Anatomy and Kinesiology

Peroneus Tertius

The peroneus tertius (perone, fibula + tertius, third) is considered misnamed by some because it is

not contained in the lateral peroneal compartment and produces ankle-foot dorsiflexion versus the

plantar flexion produced by the other peroneals. It is actually considered part of the extensor digitorum

longus, and it is considered its fifth tendon. The peroneus tertius originates from the lower fibula and

interosseus membrane and inserts onto the dorsal surface of the base of the fifth metatarsal (figure

6.14). Due to its lateral placement and the fact that it crosses in front of the ankle joint axis, its actions

are ankle-foot dorsiflexion and eversion of the foot. The peroneus tertius has been observed only in

humans and great apes, although it is not present in all humans.

Palpation: When it is present, you can palpate the tendon of the peroneus tertius just lateral to the

extensor digitorum longus tendon going to the fifth toe while performing the same movement as for

palpation of the extensor digitorum longus.

Posterior Crural Muscles

The posterior crural muscles are located on the back of the lower leg. These muscles are contained

within the superficial posterior compartment of the leg and include the gastrocnemius, soleus, and

plantaris muscles. The plantaris is considered a vestigial, rudimentary muscle that is absent in about

8% of humans (Rasch, 1989). In addition to being a weak assistant flexor of the knee, the plantaris

contributes to plantar flexion. However, because its contribution is so minimal in terms of force produc-

tion relative to the gastrocnemius and soleus (Levangie and Norkin, 2001), the plantaris will not be

discussed further in this text. The posterior crural muscles all produce ankle-foot plantar flexion and

are very important for propulsion.

Palpation: The tendon of the extensor digitorum longus can be found just lateral to the tendon of

the extensor hallucis longus at the level of the ankle. Extending toes 2 through 4 against resistance

provided by your hand will make the tendons more prominent; and while the single tendon can be

palpated near the ankle, distally the tendon divides into four parts, all of which can be palpated from

below the ankle to their attachment on the top of the toes.

Attachments and Primary Actions of Peroneus Tertius

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

Peroneus tertius

(per-o-NEE-us TER-shus)

Anterior fibula and adjacent interosseus

membrane in lower third of leg

Upper surface of base of

fifth metatarsal

A-F dorsiflexion

Foot eversion

Attachments and Primary Actions of Triceps Surae

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

Triceps surae

Gastrocnemius

(gas-truk-NEE-mee-us)

Posterior aspect of medial and

lateral condyles of femur

Posterior calcaneus via

Achilles tendon

A-F plantar flexion

(Knee flexion)

Soleus

(SO-lee-us)

Posterior aspect of upper

tibia, fibula, and interosseus

membrane

Posterior calcaneus via

Achilles tendon

A-F plantar flexion

Stabilizes lower leg on foot

Gastrocnemius

The gastrocnemius (gaster, belly + kneme, leg) is a double-bellied superficial muscle that attaches

above the knee on the medial and lateral femoral condyles and is responsible for most of the rounded

appearance or prominence of the “calf” of the leg (figure 6.15). It runs down the back of the lower leg