Disclosures: Tracey C. Isidro, MD: No financial relationships or conflicts of interest

Case Description: A 49-year-old male presented with a two-year history of intermittent, burning left knee pain after falling off his bike. When asked about his knee pain, he pointed to the fibular head and left patellar tendon. Pain was worse with repetitive dorsiflexion and 10+ minutes of walking, but better with rest. He denied radicular symptoms or paresthesia. He previously underwent a series of three L5 epidural steroid injections and a steroid injection to the knee, which provided minimal relief.

Setting: Outpatient

Patient: A 49-year-old male with knee pain. Assessment/

Results: He was tender to palpation over the left posterior fibular head and patellar tendon. He had full knee extension and strength except for left extensor hallucis longus and gluteus medius bilaterally. Special provocative knee exams were unremarkable. Radiographs showed no abnormalities. MRI demonstrated edema in the quadriceps fat pad. Electromyography of the lower extremities including the fibular nerve performed one year after date of injury were normal. Diagnostic ultrasound revealed evidence of an enlarged and entrapped fibular nerve. Pt underwent an ultrasound-guided left fibular nerve hydrodissection injection and returned to normal activities.

Discussion: In patients presenting with knee pain, one can consider fibular etiologies. The most frequent site of fibular nerve entrapment is below the knee where it wraps around the fibula, and 79% present with sensory loss while only 17% present with pain. One can also present with weakness in ankle dorsiflexion and have a resultant foot drop. EMG and nerve conduction studies are useful in determining the peripheral neuropathy, but, as in this case, a normal EMG should not rule out peripheral neuropathy entirely.

Conclusion: Fibular nerve entrapment can present as pain over the fibular head with extensor hallucis longus weakness and should be considered in the differential diagnosis of knee pain.

Level of Evidence: Level V

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PM&R Meeting Abstracts - https://pmrjabstracts.org/abstract/peripheral-neuropathy-as-knee-pain-a-case-report/