Presentation
Painful swelling in lateral aspect of knee, about six weeks previously. Symptoms subsided significantly over the time. According to patient, residual swelling at the time of ultrasound is much smaller. No distal leg complaints. No traumatic episode. Recreational sport is tennis. Referred for local swelling ultrasound.Painful swelling in the lateral aspect of the knee, about six weeks previously. Symptoms subsided significantly over time. According to the patient, residual swelling at the time of ultrasound is much smaller. No distal leg complaints. No traumatic episode. Recreational sport is tennis. Referred for a local swelling ultrasound.
Patient Data
No bony abnormality on plain radiograph of the knee (not available for publication).
In the region of pain, there is a lobulated anechoic swelling
- dimensions 25 x 12 x 9 mm.
- internal septa present
- no calcification / vascularity in lesion
- neck of lesion seen extending to proximal tibio-fibular joint
- no extension along common peroneal nerve
Common peroneal nerve
- elevated by lesion
- nerve is separate from lesion.
- no nerve edema
Lateral collateral ligament
- intact with normal echopattern
- lesion does not abut ligament
Biceps tendon
- intact with normal echopattern
- lesion does not abut tendon
Case Discussion
Active adult patient presented with localized swelling in the lateral aspect of the knee. Clinically, it was below the femorotibial joint line. Ultrasound findings favor a cyst. Its neck extends to the proximal tibiofibular joint (better appreciated with low dynamic range image, which makes black more black). Cyst elevates common peroneal nerve; however, there is no extension in or around the common peroneal nerve. There was no clinical sign of common peroneal nerve palsy.
Similar findings on follow-up MRI (imaging not available for upload).
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