Talar beak sign (talus)
The talar beak sign is seen in cases of tarsal coalition, and refers to a superior projection of the distal aspect of the talus. It is most frequently encountered in talocalcaneal coalition. It is thought to result from abnormal biomechanic stresses at the talonavicular joint.
The term bird's beak sign is used in a number of other contexts: see bird beak sign (disambiguation).
It needs to be distinguished from:
- an osteophyte due to degenerative change at the talonavicular joint
- the talar ridge found more proximally at the site of insertion of the ankle capsule ; the normal talar ridge is several millimeters high and has a straight or slightly convex, graded slope proximally, and a straight, sharp margin distally
- a hypertrophic talar ridge may be present with no coexisting coalition, e.g. in patients with DISH, acromegaly, rheumatoid arthritis or in athletes