Pes Anserinus Bursitis Mimicking L4 Radiculopathy: A Case Report

Introduction: Pes anserinus bursitis is a clinical entity associated with pain 2 – 5 cm medial and distal to the knee joint. It is a distinct clinical entity in the clinic but can however present a diagnostic dilemma in some patients being managed for radiculopathy along the L4 dermatome. Successful management of this condition in our center may provide an experience of treatment for similar presentations. Case report: A 65-year old woman with long-standing symptoms of severe canal stenosis and exiting nerve root compression was seen in the neurosurgery clinic. She had posterior lumbar interbody fusion at L4/5 and was subsequently referred to physiotherapy. Shortly after the commencement of physiotherapy, she complained of severe radicular pain around the medial knee joint. Conservative measures were taken to manage this pain but she only responded to intralesional injection of steroid. Clinical discussion: Pain in the distribution of a spinal nerve is common in the neurosurgery wards with or without surgery. This presentation in a patient after surgical intervention created a context ripe for diagnostic error as our initial clinical suspicion was directed to possible problems that resulted from the fusion surgery. Conclusion: Through this paper, we draw attention to the possible pitfalls of diagnosing radicular pain in the L4 dermatome. Careful history and examination are essential tools for the clinician especially when these symptoms present a diagnostic dilemma in the postop patient.