The experience of pain on the outside of the lower leg or ankle during walking often points toward an issue with the fibularis longus, a muscle whose tendon plays a substantial role in foot mechanics. This discomfort is often amplified by weight-bearing activities, making simple actions like walking challenging.
The Fibularis Longus Muscle and Its Function
The fibularis longus muscle, formerly known as the peroneus longus, is situated in the lateral compartment of the lower leg, running alongside the fibula bone. Its muscle belly originates high on the outside of the leg, and its long tendon descends behind the prominent outer ankle bone, the lateral malleolus. The tendon then crosses underneath the foot, attaching to the medial cuneiform and the base of the first metatarsal on the inside of the foot.
This unique path allows the fibularis longus to perform two main actions at the ankle: eversion, which tilts the sole of the foot outward, and plantar flexion, which points the foot downward. For walking, the muscle and its tendon act as a dynamic stabilizer, helping to steady the leg on the foot. This stabilizing action supports the transverse and longitudinal arches, ensuring the foot remains a stable platform during the push-off phase of gait.
Primary Causes of Fibularis Longus Pain
The most frequent source of fibularis longus pain is tendinopathy, which describes a breakdown or irritation of the tendon fibers, often due to overuse. This condition is characterized by pain and tenderness along the outside of the ankle and foot, where the tendon passes behind the lateral malleolus. The pain intensifies during weight-bearing activities like walking because the tendon is repeatedly strained as it attempts to stabilize the foot.
Another cause is peroneal tendon subluxation, where the tendon snaps or dislocates from its groove behind the ankle bone. This usually occurs when the superior peroneal retinaculum, the tissue band that holds the tendons in place, becomes torn or damaged. During walking, the tendon’s repeated movement causes friction and mechanical irritation, resulting in a distinct snapping sensation and pain.
Acute strain or tear of the fibularis longus muscle or its tendon can also cause sudden, sharp pain while walking. These tears can range from micro-tears to a full-thickness rupture, often associated with a forceful movement of the foot, such as a severe ankle sprain. Because the muscle is unable to generate the force needed for eversion and arch support, the act of pushing off the ground during the gait cycle becomes painful and difficult. High arches, or a sudden increase in activity level, can contribute to these overuse injuries.
Immediate Strategies for Acute Relief
When acute fibularis longus pain flares up, the goal is to reduce inflammation and protect the tendon from further stress. Temporarily switching to non-weight-bearing activities gives the tendon a chance to rest and begin the healing process.
The R.I.C.E. protocol—Rest, Ice, Compression, and Elevation—provides a structured approach for managing pain in the first 24 to 72 hours following an acute injury. Applying ice to the outer ankle area for about 15 to 20 minutes several times a day helps to constrict blood vessels and limit swelling. Gentle compression with an elastic bandage helps control edema, while elevating the foot above heart level assists in draining excess fluid.
Over-the-counter nonsteroidal anti-inflammatory drugs (NSAIDs) may also be used to help manage pain and reduce localized inflammation. However, this should only be done after consulting a healthcare professional.
Long-Term Rehabilitation and Strengthening
Moving beyond the acute phase requires a structured rehabilitation program focused on restoring strength and preventing recurrence. Specific exercises, such as targeted ankle eversion against the resistance of a therapy band, are used to strengthen the fibularis longus muscle directly. This motion, which involves turning the foot outward, should be performed slowly and controlled, ensuring the movement originates from the ankle rather than the hip.
Weight-bearing exercises are introduced gradually to improve the tendon’s tolerance to stress, which is crucial for walking without pain. Single-leg balance drills and heel raises, especially those performed while focusing on keeping pressure on the big toe, help retrain the fibularis longus to stabilize the foot during functional movements.
Appropriate footwear and orthotic support play a significant part in long-term management by addressing underlying biomechanical issues. For individuals with high arches, custom or over-the-counter orthotics can help maintain the foot’s proper alignment and reduce excessive strain during the gait cycle. Wearing supportive shoes that provide adequate ankle stabilization can prevent the foot from rolling inward, which lessens the workload on the fibularis longus tendon.