Rupture of the central extensor tendon slip. A fluid-filled gap is shown between the thickened, retracted central slip of the extensor tendon and its insertion site at the base of the middle phalanx. The tendon was retracted approximately 1cm from its insertion site.
Increased separation of the lateral extensor tendon slips. Distally, the tear of the central slip is shown to extend across its width in the right image. The lateral slips can be seen as echogenic structures at the margins of the proximal phalanx. Hyperflexion of the PIP has forced them further apart.
The RCL is thick and hypoechoic indicating a minor sprain. There is a small hypoechoic defect at the distal part of the UCL indicating a mild to moderate sprain. The palmar plate of the PIP is not seen and there is an effusion from the joint suggesting palmar plate rupture.