Proximal tibio-fibular joint cyst

Case contributed by Dr Maulik S Patel


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.

Patient Data

Age: 35 yrs
Gender: Male

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 lateral aspect of knee. Clinically, it was below femoro-tibial joint line. Ultrasound findings favor a cyst. Its neck extends to proximal tibio-fibular 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 common peroneal nerve.

Similar findings on follow-up MRI (imaging not available for upload).


PlayAdd to Share

Case information

rID: 54474
Published: 11th Jul 2017
Last edited: 14th Aug 2019
Inclusion in quiz mode: Included

Updating… Please wait.

 Unable to process the form. Check for errors and try again.

 Thank you for updating your details.