Takeaway: Weakness, poor mobility, or lack of control of the fibularis longus and other ankle muscles may contribute to injuries such as lateral ankle sprains or chronic conditions such as tendinitis, shin splints, or plantar fasciitis.
Spinalis
Attachments
• Origin: Head and lateral two-thirds of the fibula
• Insertion: Lateral sides of the first metatarsal and medial cuneiform
Actions
• Plantar flexes the ankle
• Everts the foot
Innervation
• Superficial fibular nerve
• L5-S1
The fibularis longus is a muscle located along the full length of the lateral leg. It is contained within the lateral compartment along with the fibularis brevis muscle.
The muscle belly is relatively superficial and originates on the head and proximal portion of the lateral fibula. Moving distally, its tendon runs behind the lateral malleolus, extends from lateral to medial across the bottom of the foot, and inserts near the anterior tibialis on the medial side. Together, the fibularis longus and anterior tibialis muscles form a structure called the anatomical stirrup, describing the way the two muscles sling around the bottom of the foot. This structure helps support medial arch and control movement of the foot from side to side.
The location of the fibularis longus allows it to contribute to ankle plantar flexion, as well as strongly perform ankle eversion. The fibularis brevis is a synergist in both motions, where the fibularis tertius is synergistic in ankle eversion alone. The tertius is positioned more anteriorly, giving it leverage for ankle dorsiflexion rather than plantar flexion like the longus and brevis.
Ankle eversion helps position the foot before planting it on the ground during gait and is also used when moving the body from side to side. The fibularis longus, along with the other fibularis muscles, helps 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. 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 fibularis muscles, along with the hip abductors, to power the movement. Weakness, poor mobility, or lack of control of the fibularis longus and other ankle muscles may contribute to injuries such as lateral ankle sprains or chronic conditions such as tendinitis, shin splints, or plantar fasciitis.
Palpating the Fibularis Longus
Positioning: client supine or seated with the knees extended.
Standing at the client’s feet, locate the lateral surface of the head of the fibula with your thumb.
Palpate distally onto the muscle belly of the fibularis longus.
Continue to palpate distally, following the tendon behind the lateral malleolus.
Resist as the client everts the ankle to ensure proper location.
Passive Stretch of the Fibularis Longus
Positioning: client supine or seated with the knees extended.
Stand at the client’s side and grasp the foot with one hand and stabilize the leg with the other.
Instruct the client to remain relaxed as you move the foot medially toward the other foot.
Locate the end range of ankle inversion and/or the point of gentle stretch on the fibularis longus muscle and hold for several seconds.
Return to neutral position and repeat.
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 (New York: Jones & Bartlett Learning, 2010; jblearning.com). Contact her at christy_cael@hotmail.com.