The three muscles that form the peroneal group—peroneus longus, peroneus brevis, and peroneus tertius—are located on the lateral leg. The peroneus longus and brevis are within the lateral compartment, while the peroneus tertius is part of the anterior compartment. The bellies of all three muscles are somewhat superficial along the fibula. The peroneus longus is most proximal, originating on the lateral condyle and proximal portion of the lateral fibula. The peroneus brevis begins more distal on the lateral fibula and lies deep to the longus. The peroneus tertius also begins more distal, but lies anterior between the peroneus longus and the extensor digitorum longus.
The tendons of both the peroneus longus and brevis run behind the lateral malleolus. The longus extends from lateral to medial across the bottom of the foot, and inserts near the anterior tibialis. The brevis terminates on the plantar aspect of the tuberosity at the base of the fifth metatarsal. The tendons are separated by the peroneal tubercle of the calcaneus, and both insert on the plantar surface of the foot. Because of this, they contribute to ankle plantarflexion, though the longus is more effective in this action. The tendon of the peroneus tertius runs in front of the lateral malleolus and inserts on the top of the base of the fifth metatarsal. This dorsal insertion allows it to dorsiflex the ankle.
The peroneal muscles all evert the ankle, which helps position the foot prior to planting it on the ground during gait. This motion is also used when moving the body from side to side, where the peroneals help pull the center of gravity from medial to lateral over the planted foot. This side-stepping movement is common when walking over and around objects—for example, when hiking. Ankle eversion also helps initiate and control direction changes. Activities that require pushing with the legs from side to side, like skiing and skating, rely on the peroneals, along with the hip abductors, to power the movement. Weakness, poor mobility, or lack of control of the peroneals may contribute to injuries such as lateral ankle sprains, or chronic conditions such as tendinitis or plantar fasciitis.

Peroneal Group
Attachments
• Origin: Proximal portion of the lateral fibula (longus and brevis) and distal third of the anterior fibula (tertius)
• Insertion: Lateral sides of first metatarsal and medial cuneiform (longus); lateral side of tuberosity (brevis); dorsal surface at base of fifth metatarsal (tertius)
Actions
• Plantarflexes the ankle (longus and brevis)
• Dorsiflexes the ankle (tertius)
• Everts the foot (all)
Innervation
• Superficial peroneal nerve (longus and brevis)
• Deep peroneal nerve (tertius)
• L4–S1

Palpating the Peroneals
Position: client supine.
1. Standing at the client’s feet, locate the lateral surface of the head of the fibula with your thumb.
2. Palpate distally onto the muscle belly of the peroneus longus, then follow to the brevis.
3. Palpate just anterior to the lateral malleolus to locate the peroneus tertius.
4. Continue to palpate distally, following the tendons behind, or in front of, the lateral malleolus.
5. Resist as the client everts the ankle to ensure proper location.

Client Homework: Seated Butterfly Stretch
1. Sit tall, with the soles of your feet pressed together, and knees dropped to the sides but relaxed.
2. Grasp the tops of your feet and gently roll your ankles, pulling the soles of your feet upward.
3. Keep your back, hips, and knees relaxed, focusing the stretch on the outer leg and ankle.
4. Gently hold until you feel a release in the ankle and leg.

Editor’s note: The Client Homework element in Functional Anatomy is intended as a take-home resource for clients experiencing issues with the profiled muscle. The stretches identified in Functional Anatomy should not be performed within massage sessions or progressed by massage therapists, in order to comply with state laws and maintain scope of practice.

Christy Cael is a licensed massage therapist and certified strength and conditioning specialist. Her private practice focuses on injury treatment, biomechanical analysis, craniosacral therapy, and massage for clients with neurological issues. She is the author of Functional Anatomy: Musculoskeletal Anatomy, Kinesiology, and Palpation for Manual Therapists (Lippincott Williams & Wilkins, 2009). Contact her at functionalbook@hotmail.com.

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