Can a Small Chronic Tear in the Peroneal Brevis Tendon Cause Sural Nerve Irritation?
Yes, a small chronic tear of the peroneus brevis tendon can potentially cause sural nerve irritation, though this is an indirect and relatively uncommon mechanism that occurs through local inflammation, tenosynovitis, and anatomical proximity rather than direct nerve injury.
Anatomical and Pathophysiological Basis
The sural nerve runs in close anatomical proximity to the peroneal tendons along the lateral ankle. When a chronic peroneus brevis tear is present, several mechanisms can lead to nerve irritation:
- Inflammatory response: Chronic tendon tears generate persistent local inflammation and tenosynovitis, which can create a hostile environment affecting adjacent neural structures 1
- Space-occupying effect: Tendon thickening, scarring, and adhesions from chronic tears can compress or tether the sural nerve in the confined retromalleolar space
- Traction injury: The guideline evidence specifically notes that "delayed response time of the peroneal muscle has been detected, possibly due to traction injury of the peroneal nerve" in lateral ankle injuries 2, establishing precedent for nerve involvement in peroneal pathology
Clinical Context and Evidence
The ACR Appropriateness Criteria emphasize that up to 34% of asymptomatic patients may have a tear of the peroneus brevis tendon 1, and MRI evidence of peroneal tendon pathology has only a 48% positive predictive value for clinical findings 1. This means:
- Not all peroneus brevis tears cause symptoms
- When symptoms occur, they may include nerve-related complaints if inflammation extends to adjacent structures
- Clinical examination remains paramount in determining whether the tear is actually causing the patient's symptoms
Diagnostic Approach
To determine if the peroneus brevis tear is causing sural nerve irritation:
Physical examination findings to assess:
- Tenderness along the sural nerve distribution (lateral foot and ankle)
- Positive Tinel's sign along the sural nerve course
- Sensory changes in the lateral foot/fifth toe
- Pain with resisted eversion (tendon pathology)
- Tenderness posterior to the lateral malleolus
Imaging considerations:
- MRI demonstrates peroneal tendinopathy with 83.9% sensitivity and tendon tears with 54.5% sensitivity 1
- Ultrasound shows 100% sensitivity and 90% accuracy for peroneal tendon tears and can assess dynamic subluxation 1
- Look for associated tenosynovitis and fluid collections that could compress the nerve
Diagnostic injection:
- US-guided or fluoroscopy-guided intra-sheath anesthetic injection can help differentiate tendon pain from nerve pain 1
- If symptoms persist after tendon sheath injection, nerve involvement is more likely
Important Caveats
The sural nerve is more commonly injured through:
- Direct surgical trauma (well-documented complication of peroneal tendon surgery) 3
- Traction during Achilles tendon ruptures 4
- Ankle sprains with inversion mechanisms 2
Rather than from chronic tendon tears themselves. The connection between a small chronic peroneus brevis tear and sural nerve symptoms is therefore more likely to be:
- Coincidental (both pathologies present but unrelated)
- Secondary to shared inflammatory processes
- Related to altered biomechanics causing nerve traction
Clinical Recommendation
If a patient presents with lateral ankle pain and both a peroneus brevis tear and sural nerve symptoms:
- Perform diagnostic injection into the peroneal tendon sheath to isolate the pain source
- If symptoms resolve completely, the tear is the primary problem
- If sensory symptoms persist, consider the sural nerve as a separate or co-existing pathology requiring specific management
- Recognize that treating the tendon tear alone may not resolve nerve symptoms if true neuropathy exists
The key is recognizing that while anatomical proximity makes nerve irritation possible, it is not the typical presentation of isolated peroneus brevis tears, and both conditions may require independent assessment and treatment.