Anatomy of posteromedial corner of the knee.

An axial plane illustration of the knee at the level of the menisci demonstrates the components of the posteromedial corner. At this level the semimembranosus (SM) can be seen contributing fibers to the oblique popliteal ligament (OPL) and to the posterior capsule. The posterior oblique ligament (POL) is found between the superficial medial collateral ligament (SMCL) and the semimembranosus tendon on this view. The medial head of the gastrocnemius muscle (MG), sartorius muscle (SA), gracilis tendon (G) and semitendinosus tendon (ST) are also indicated.

An axial fat-suppressed proton density-weighted image in a 13 year old following a fall with twisting reveals soft tissue thickening and edema throughout the region of the POL (arrows). The low signal intensity SMCL (arrowhead) is visible anterior to the region of the POL. Marrow edema (asterisk) is visible within the medial femoral condyle as well. The medial gastrocnemius tendon (MG) and the semimembranosus tendon (SM) are unaffected.

Axial fat-suppressed proton density images in a 15 year-old with medial pain demonstrate avulsive marrow edema within the medial epicondyle (asterisks), at the expected attachment site of the POL. There is edema and soft tissue thickening in the region of the POL (arrows).

Axial fat-suppressed proton density-weighted images in a 28 year-old female with posteromedial pain reveals fluid and edema compatible with partial tearing at the tendon origin of the medial head of the gastrocnemius (arrows).

An axial fat-suppressed proton density-weighted image in a 25 year-old who had a hyperextension injury with PCL disruption. There is diffuse posteromedial edema in the region of the POL(arrowheads), and the SM is thickened and edematous (arrow) compatible with partial tearing.

A T2 weighted sagittal image in a 43 year-old with medial pain and swelling reveals lobulated fluid within the pes anserine bursa (arrows), compatible with bursitis. The medial gastrocnemius origin (arrowhead) and the SM tendon (SM) are unaffected.

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