The classical imaging features in anterior impingement are divided into bony and soft tissue findings.
The commonest bony abnormalities are :
• a spur on the anterior aspect of the distal tibia
• just to the lateral side of the mid line,
• a spur, divot or combination of both of these on the dorsal aspect of the talus.
• effusion, synovial thickening and fibrosis in the anterior joint space .
The two bony findings do not always correspond in location (i.e. they are not always “kissing osteophytes”) as the more common location for the talar bone changes are just medial to the midline.
The imaging diagnosis of anterior impingement is made on a combination of plain film and cross sectional imaging findings. The lateral plain radiograph will demonstrate the bony findings and exclude associated arthritis. An oblique anteromedial view, with the beam tilted 45 degrees craniocordal and the leg in 30 degrees of external rotation may demonstrate the anteromedial talar osteophyte to greater effect. This is not necessary if ultrasound is available, as all of the features are readily apparent.
US and MRI demonstrates an increase in size with displacement of the anterior fat pad. Simple effusion can be distinguished from synovial reaction by the presence of increased reflectivity or complexity on MRI within the synovium.
Dynamic UD demonstrates the actual impingement and provides useful correlation with patient’s symptoms.
