Posterior ankle impingement syndrome (Os trigonum syndrome)

Clinical History:
42 year old woman with right heel pain that started 6-8 months ago.

Posterior ankle impingement syndrome

MR Technique:
3T Scanner (Siemens Verio) with foot and ankle coil: Image 1: Sagittal T2 turbo spin echo (TR/TE 4170/97 ms, slice thickness 3 mm, scan time 4 min 2 sec) ; Image 2: Sagittal T1 (TR/TE 700/20 ms, slice thickness 3 mm, scan time 1 min 51 sec); Image 3 and 4: Coronal STIR TI 220, TR/TE 5800/32, slice thickness 3 mm, scan time 2 min 48 sec).

Imaging Findings:
Large os trigonum is seen with edema in the os. Swelling and edema is also seen in the posterior soft tissues and posterior ligamentous complex. Coronal STIR (image 4) shows edema in the posterior talofibular ligament.