Ankle and heel pain is a common complaint. Patients often are surprised to discover their pain is caused by trigger points in the fibularis tertius, a small and easily overlooked muscle in the front of the lower leg. This article will review the anatomy of the fibularis tertius muscle and discuss the trigger points that cause lateral ankle and heel pain, as well as treatment techniques and ways to educate your patients about the causes of their pain.

The name of this muscle has changed over the years. Fibularis tertius has replaced the older term, peroneus tertius. Peroneal was derived from the Greek terminology meaning "a pin." Pointed objects like sewing needles were termed perone by the Greeks. The Latin word fibula also means "a pin or skewer." In some animals, the fibula often is very narrow and has sharp tips (styloid processes), thus it is probable that this bone was named for its resemblance to a pin, or sewing or knitting needle. Tertius is the Latin word for "third," or "concerning the third." This muscle attaches to the lower third of the fibula and is one of three muscles attaching to the fibula that everts the foot.

The lower leg contains two bones: the tibia and fibula. The tibia, the bone on the medial side, is the larger weight-bearing bone and forms the medial malleolus. The fibula, the smaller slender bone on the lateral side, is not a weight-bearing bone and forms the lateral malleolus.

The leg is divided into three fascial compartments: anterior, posterior and lateral. The fibularis tertius is located in the anterior compartment, whereas the lateral compartment contains the fibularis longus and brevis. The interosseous membrane that runs between the fibula and tibia divides the anterior and posterior compartments. The anterior intermuscular septum divides anterior and lateral compartments. The posterior intermuscular septum divides posterior and lateral compartments. (See Photo 1) Proximally, the fibularis tertius attaches to the distal third of the anterior surface of the fibula, the interosseous membrane and the adjacent intermuscular septum. In the foot, it attaches on the dorsum of the base of the fifth metatarsal. (See Photo 2)

Action

The primary actions of the fibularis tertius are dorsiflexion of the ankle and eversion of the foot. The fibularis tertius dorsiflexes the ankle along with three other muscles: fibularis longus, fibularis brevis and tibialis anterior. It also acts to evert the foot, assisting fibularis longus and brevis.

It is important to assess, treat, lengthen and strengthen, as appropriate, the synergistic and antagonistic muscles that cross the joint. A muscle-movement chart is a quick reference tool that groups joints by body region and then lists the muscles that create each specific joint movement. A muscle movement chart also shows the degrees of normal range of motion (ROM) for each joint. This information provides a list of muscles to target and helps therapists develop a comprehensive treatment plan with goals that include improving ROM.

Trigger Points

Patient complaints typically include weakness in the ankle and/or pain and tenderness in the ankle, behind and over the lateral malleolus. Whenever a patient reports a trigger point during treatment, take a moment to show them the specific referral pattern on a trigger point chart. Utilizing charts as visual aids to educate your patients about trigger point patterns is a powerful way to demonstrate your knowledge and understanding of the patient's pain. (See "Tools to Succeed for Massage Therapists," MT May 2009.)

Trigger points in the fibularis tertius muscle usually are palpated proximal and anterior to the lateral malleolus. The referral pattern for fibularis tertius trigger points is "pain and tenderness along the anterolateral aspect of the ankle with a spillover patterns projecting downward behind the lateral malleolus to the lateral aspect of the heel."¹ (See Photo 3)

There are many reasons trigger points form in the fibularis tertuis. Sometimes they are caused by activities and/or events that occurred months, years or even decades before the onset of the chronic pain. A few examples include inversion sprains of the ankle, wearing too-tight running shoes, work boots or ski boots, direct trauma, a new activity requiring overuse of the muscle, and weakness from prolonged periods of immobility due to injury.

Postural analysis photos will reveal the stresses patients place on their muscles. (See "Getting Comfortable with Postural Analysis," MT July 2008) Intake forms, postural analysis, gait evaluation and orthopedic assessments will help you uncover a lot of information that will prepare you for the hands-on treatment.

Muscle Test: Palpation of the bony landmarks coupled with muscle testing will ensure you are specifically isolating and thoroughly treating the correct muscle. To muscle test the fibularis tertius, place the patient in a supine or sitting position. Support the patient's leg with one hand just above the ankle joint so your palm is cradling the Achilles tendon. With the other hand, apply pressure against the lateral side and dorsal surface of the foot with pressure in the direction of plantar flexion of the ankle and inversion of the foot. Instruct the patient to dorsiflex the ankle and evert the foot while you apply resistance.

Check for Sensitivity: Palpate along the belly and tendon of the muscle to check for sensitivity. Treatment should not cause pain.

Fifth Metatarsal: Treat the tendon attachment on the dorsal surface of the base of the fifth metatarsal. Apply static pressure and then integrate muscle-fiber and cross-fiber techniques. Start on the base of the fifth metatarsal and follow the tendon anterior to the lateral malleolus. (See Photo 4)

Tendon: Apply lubrication to the skin. Using distal to proximal gliding strips on the muscle, follow the tendon along the front of the lateral malleolus.

Belly: Glide distal to proximal on the belly of the muscle. Treat the attachment on the anterior lower third of the fibula. (See Photo 5)

Conclude your sessions with a brief explanation of the problems you identified and how ongoing massage therapy can help. Tell your patients you will design a customized treatment plan to address the soft-tissue components of their pain, and educate them on the use of ice, heat and other methods of self-care. Provide a stretching routine so patients can continue to improve and maintain themselves between visits. Show your patients proper home and work ergonomics (using computers and phones, lifting, etc.).

I wish you best in the treatment room. Please drop me a line to tell me about your results.

Reference

1. Simons DG, Travell JG. Myofascial Pain and Dysfunction, The Trigger Point Manual: The Lower Extremities. Baltimore: Lippincott, Williams and Wilkins, 1992.