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Knee LCL Sprain

LCL Sprain Results from a blow to the medial knee that places tensile forces on the lateral structures or by internal rotation of the tibia on the femur. It result in varus laxity of the knee.

LCL injury is frequently associated with damage to the posterolateral corner, the isolated injury is rare.

See Also: MCL Sprain

Related Anatomy

The lateral collateral ligament (LCL) does not attach to the joint capsule or meniscus. It’s a cordlike structure arises from the lateral femoral epicondyle, sharing a common site of origin with the lateral joint capsule, and inserts on the proximal aspect of the fibular head.

The LCL is the primary restraint against varus forces when the knee is in the range between full extension and 30 degrees of flexion. This structure also provides a primary restraint against external tibial rotation and a secondary restraint against internal rotation of the tibia on the femur.

The blood supply is from superolateral and inferolateral geniculate arteries.

See Also: Knee Ligaments Anatomy
LCL anatomy

LCL Sprain Classification

LCL Sprain is classified based on the lateral joint opening as compared with the normal contralateral knee
with varus stress:

  1. Grade I: 0-5 mm lateral opening.
  2. Grade II: 6-10 mm lateral opening.
  3. Grade III: >10 mm lateral opening without an endpoint.

It’s also classified based on the amount of ligamentous disruption:

  • Grade I: minimal tear.
  • Grade II: partial tear.
  • Grade III: complete tear.

LCL Sprain Symptoms

The patient with a LCL Sprain complains of acute pain on lateral joint line of the knee, fibular head, or femoral condyle, depending on the location of the sprain..

Swelling, if present, is likely to be localized, especially when trauma is isolated to the LCL, because it is an extracapsular structure.

Palpation eliciting tenderness along the length of the LCL and possibly the lateral joint line.

The extracapsular nature of the LCL gives it a normally “springy” end-feel. A varus stress test result that feels empty when compared with the contralateral side should be considered a positive result for an LCL sprain.

Because a varus force with concurrent tibial rotation can cause damage to other structures, injuries to the posterolateral corner, ACL, and/or PCL as well as posterolateral rotational instability must be suspected in patients suffering from Lateral Collateral Ligament Sprain.

Because of the relative proximity of the peroneal nerve, patients suspected of having suffered an injury to the lateral or posterolateral aspect of the knee require careful evaluation of distal function of the common and superficial peroneal nerve, especially if an associated fracture of the fibular head is suspected.

See Also: Varus Stress Test


AP, lateral, and varus stress radiographs are recommended.

A T2-weighted MRI can demonstrate tearing of the Knee LCL Sprain and/or associated meniscal injury.

LCL injury MRI
LCL injury seen on MRI

Knee LCL Sprain Treatment

Although the LCL is an extracapsular and extra-articular structure, the ligament still relies on synovial fluid for much of its nutrition.

In many cases, even complete LCL ruptures are treated nonoperatively with limited immobilization, progressive ROM, and functional LCL sprain rehabilitation in Grade I, II LCL injury.

However, the LCL’s relatively poor healing properties and the ligament’s importance in providing rotational stability to the knee often necessitate early surgical repair or late reconstruction (LCL repair/reconstruction +/- PLC / ACL/ PCL reconstruction).

LCL Sprain treatment algorithm
LCL Sprain Treatment Algorithm
LCL Sprain rehabilitation
LCL Sprain rehabilitation


  1. Murakami Y, Ochi M, Ikuta Y, Higashi Y. Quantitative evaluation of nutritional pathways for the posterior cruciate ligament and the lateral collateral ligament in rabbits. Acta Physiol Scand. 1998 Apr;162(4):447-53. doi: 10.1046/j.1365-201X.1998.00291.x. PMID: 9597110.
  2. Zorzi, C, et al: Combined PCL and PLC reconstruction in chronic posterolateral instability. Knee Surg Sports Traumatol Arthrosc, 21:1036, 2013.
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