Hyperextension knee injury - posteromedial and posterolateral corner injuries

Case contributed by Dr Yuan Ling

Presentation

Traumatic hyperextension injury playing football.

Patient Data

Age: 25 years
Gender: Male

Osteochondral impaction anterior aspect medial compartment (MFC/MTP).
Further bone bruising anterior LTP. No meniscal tear.
Presumed contusion of posterior aspect infrapatellar fat pad.
Posterior capsule torn, partial tear PCL posteromedial bundle.

Semimembranosus tendon (SMT) rupture with retraction/recoil. Small remnant stump.
Disruption of SMT contribution to the oblique popliteal ligament.
Partial tear origin of posterior oblique ligament (POL). Intact MCL.
Separation of layer 1 (crural fascia, sartorius) from layer 2 (superficial MCL, POL, SMT).

High grade tear LCL origin, partial tear popliteus tendon origin.
Partial tear biceps femoris insertion (fibular arm torn, tibial arm intact).
Torn arcuate and popliteofibular ligaments, anteroinferior meniscopopliteal fascicle.

Case Discussion

The semimembranosus tendon (SMT) has a complex insertion and forms an integral part of the posteromedial corner:

  • direct: common SMT to posterior aspect MTP 1 cm below joint
  • anterior: common SMT posteromedial to MTP, inserts deep to MCL
  • oblique popliteal ligament: blends with the OPL
  • posterior oblique ligament: blends with sheath of SMT
  • meniscal: SMT to coronary ligament of medial meniscus posterior horn
  • distal expansion: over popliteus muscle (also called popliteal aponeurosis)

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