Peroneal Strain

What Is It?

The peroneal (fibularis) muscles run down the outside of the lower leg and turn the foot outward, protecting against ankle sprains. They strain with overuse or alongside an inversion injury.

A strain means muscle fibers were overstretched. We grade strains I–III: Grade I — mild, microscopic fiber injury; Grade II — moderate, a partial tear with strength loss; Grade III — severe, complete disruption.

How It Happens

Running on uneven ground, a partial ankle-rolling episode, or a rapid increase in training on cambered surfaces.

What It Feels Like

Pain along the outside of the lower leg or behind the outer ankle bone, worse with pushing the foot outward against resistance or walking on uneven ground.

How Long Recovery Takes

• Grade I: 1–2 weeks
• Grade II: 3–6 weeks
• Grade III: 6–10 weeks

Treatment

Almost all muscle strains heal without surgery. For the first 72 hours: relative rest, ice 15–20 minutes several times daily, compression, and gentle motion — complete rest slows healing. Then a progressive program: pain-free motion → isometrics → strengthening → eccentric loading (strengthening the muscle while it lengthens — the phase that prevents re-injury) → sport-specific work.

Resisted eversion strengthening and single-leg balance work — the same program that protects against ankle sprains.

Returning to Sport

Return when strength is at least 90% of the other side, motion is full and pain-free, and you can perform your sport’s movements at full speed without hesitation. Returning before the muscle is re-strengthened is the main cause of re-injury.

Preventing the Next One

Balance training, appropriate footwear, and gradual introduction of trail running.

When to Call Us

A snapping sensation behind the outer ankle bone with the tendon visibly flipping suggests peroneal tendon subluxation — a different problem that needs specific evaluation.