FCL (Fibular Collateral Ligament)

FCL (Fibular Collateral Ligament). The FCL, also known as the lateral collateral ligament, is the primary static stabilizer to varus opening of the knee in the initial 0-degree to 30-degree arc of knee flexion. With knee flexion beyond 30 degrees, the FCL
becomes slightly lax.4 In addition, this ligament provides resistance to external rotation of the tibia, primarily near extension. The femoral origin of the FCL is extracapsular and easily identified by palpating the lateral epicondyle. LaPrade et al9 have shown that the femoral insertion of the FCL consistently lies 1.4mm proximal and 3.1mm posterior to the lateral epicondyle.  This location may be palpated as a small bony depression formed between the lateral epicondyle and the supracondylar process. The FCL is approximately 70mm long and its primary distal insertion site is the lateral aspect of the fibular head.
 

FIGURE 3. Removal of the long head of the biceps femoris tendon reveals components of the short head of the biceps
(SHB): capsular arm (Cap arm), direct arm (Dir arm), anterior arm (Ant arm), and lateral aponeurosis (LatAp). F, femur; FCL, fibular collateral ligament; LM, lateral meniscus; M 1/3, the midthird lateral capsular ligament; T, tibia. Reprinted with permission.16

During a surgical approach, the FCL can be easily identified through a small 3-cm incision made parallel to the fibers of the long head of the biceps femoris tendon. This incision is made superficial to the proximal extent of the fibular head and should release the insertion of the anterior arm of the long head of the biceps femoris tendon.6 This incision should readily expose the biceps bursa, which forms an inverted ‘‘J’’ shape around the anterior and anteromedial portions of the FCL. The biceps bursa encapsulates the distal 25% of the FCL.
The long head of the biceps femoris tendon forms the lateral border of the biceps bursa.8 The fibular insertion of the FCL lies 8.2mm posterior to the anterior border of the fibula, and 28.4mm antero-inferior to the proximal tip of the fibular styloid.17,23 On average, this comprises 38% (13.9 mm) of the total width of the fibular head, which measures 36.6mm anterior to posterior.6,9