Lateral Collateral Ligament Injury

The lateral collateral ligament runs from the lateral femoral epicondyle to the fibular head and resists varus stress. It forms the posterolateral corner with the popliteus tendon and the popliteofibular ligament. Isolated injuries are uncommon (under 2% of knee ligament injuries), and most occur as part of a posterolateral corner injury or multiligament knee injury.

Mechanisms are a varus blow to the anteromedial knee, hyperextension and a non-contact twist. Grading by lateral opening at 30 degrees: grade I under 5 mm, grade II 5 to 10 mm, grade III over 10 mm. Common peroneal nerve palsy occurs in 15 to 29% of posterolateral corner injuries and popliteal artery injury in a minority. Untreated posterolateral instability causes varus thrust gait, cruciate graft failure and early lateral compartment arthritis.

• Lateral knee pain, swelling and a feeling of instability on uneven ground
• Varus stress laxity at 30 degrees (and at 0 degrees if the cruciate is also torn)
• Dial test positive (over 10 degrees increase in external rotation at 30 degrees), reverse pivot shift and external rotation recurvatum
• Varus thrust gait, lateral bruising
• Foot drop and reduced sensation of the first web space (peroneal nerve)
• Red flags: foot drop, cool limb, gross instability, associated cruciate rupture

• Examination: varus stress, dial test, neurovascular assessment including ankle brachial index when a dislocation is suspected.
• Radiographs: fibular head avulsion (arcuate sign), lateral tibial plateau fracture.
• Varus stress radiographs: side-to-side lateral gap difference of 2.7 mm suggests isolated lateral collateral injury, and 4 mm or more indicates complete posterolateral corner injury.
• MRI with high resolution lateral coronal oblique images.
• Nerve conduction studies and EMG at 3 to 4 weeks for foot drop.

Differentials: biceps femoris injury, iliotibial band syndrome, lateral meniscal tear, popliteus injury, fibular head fracture.

Grades I and II isolated: hinged brace for 4 to 6 weeks, early range of motion, ibuprofen 400 mg orally every 8 hours with food for 5 to 7 days, and strengthening.

Grade III and posterolateral corner injuries:

• Acute repair within 2 to 3 weeks when tissue quality permits, with graft augmentation.
• Chronic or irreparable: anatomic reconstruction with two grafts (fibular and popliteus limbs, for example semitendinosus autograft or Achilles allograft).
• Fix coexisting cruciate injury. Correct varus malalignment with a high tibial osteotomy first when the limb alignment is varus.
• Cefazolin 2 g IV before incision.
• Rehabilitation: non-weight-bearing for 6 weeks, motion limited to 0 to 90 degrees for 6 weeks, return to sport at 9 to 12 months.

Peroneal nerve palsy: ankle foot orthosis. Neurolysis or repair when there is no recovery by 3 to 6 months, and tibialis posterior tendon transfer for persistent drop foot.

Complications: residual laxity, stiffness, nerve injury, graft failure.

Follow up at 2 weeks, 6 weeks, 3 months, 6 months and 12 months.