The Anterolateral Complex of the Knee

Abstract

Background: Significant controversy exists regarding the anterolateral structures of the knee.

Purpose: To determine the layer-by-layer anatomic structure of the anterolateral complex of the knee.

Study design: Descriptive laboratory study.

Methods: Twenty fresh-frozen cadaveric knees (age range, 38-56 years) underwent a layer-by-layer dissection to systematically expose and identify the various structures of the anterolateral complex. Quantitative measurements were performed, and each layer was documented with high-resolution digital imaging.

Results: The anterolateral complex of the knee consisted of different distinct layers, with the superficial and deep iliotibial band (ITB) representing layer 1. The superficial ITB had a distinct connection to the distal femoral metaphysis and femoral condyle (Kaplan fibers), and the deep layers of the ITB were identified originating at the level of the Kaplan fibers proximally. This functional unit, consisting of the superficial and deep ITB, was reinforced by the capsulo-osseous layer of the ITB, which was continuous with the fascia of the lateral gastrocnemius and biceps femoris muscles. These 3 components of the ITB became confluent distally, and the insertion spanned from the Gerdy tubercle anteriorly to the lateral tibia posteriorly on a small tubercle (lateral tibial tuberosity). Layer 3 consisted of the anterolateral capsule, in which 35% (7/20) of specimens had a discreet mid-third capsular ligament.

Conclusion: The anterolateral complex consists of the superficial and deep ITB, the capsulo-osseous layer of the ITB, and the anterolateral capsule. The anterolateral complex is defined by the part of the ITB between the Kaplan fibers proximally and its tibial insertion, which forms a functional unit. A discrete anterolateral ligament was not observed; however, the anterolateral ligament described in recent studies likely refers to the capsulo-osseous layer or the mid-third capsular ligament.

Clinical relevance: The anterolateral knee structures form a complex functional unit. Surgeons should use caution when attempting to restore this intricate structure with extra-articular procedures designed to re-create a single discreet ligament.

Keywords: ITB; anatomy; anterolateral; capsule; capsulo-osseous layer; iliotibial band; knee; pivot shift.

Figure 1.

Layer 1 including the superficial iliotibial band (sITB) and iliopatellar band (IPB). Asterisks indicate the folding of the posterior part of the sITB at higher degrees of knee flexion. GT, Gerdy tubercle.

Figure 2.

Posterior reflection and distal release of the superficial iliotibial band (ITB) revealed the obliquely aligned fibers of the middle layer of the ITB (mITB). As seen here, these fibers could best be seen in the supracondylar region. dITB, deep layer of the ITB.

Figure 3.

Reflection of the superficial iliotibial band (sITB) revealed its firm attachment to the distal femoral metaphysis via the Kaplan fibers (KF). The KF are in close proximity to the branches of the superior genicular artery (white arrowhead) and have accessory insertions (asterisk) proximal and anterior to the femoral epicondyle. Further, the superficial layer of the anterolateral capsule becomes visible.

Figure 4.

(A) With further posterior reflection of the superficial iliotibial band (sITB) and blunt separation from the deeper layers, the capsulo-osseous layer (black arrowhead) can be appreciated. The white arrowhead indicates the branches of the superior genicular artery. (B) Proximal, the longitudinally aligned fibers of the intermuscular septum (IS) can be differentiated from the Kaplan fibers (KF). Further, retraction of the sITB reveals the deep ITB (dITB), which merges with the sITB distally. No distinct anterolateral ligament could be observed. The asterisk highlights the accessory insertion of the KF.

Figure 5.

Removal of the anterolateral soft tissues showed the insertions and origins of the different layers of the iliotibial band (purple ink). The tibial insertion of the capsulo-osseous layer on the lateral tibial tuberosity (dotted circle) is located about halfway between the Gerdy tubercle (GT) and the fibular head. On the femoral side, the capsulo-osseous layer is continuous with the fascia of the lateral gastrocnemius tendon (white arrowhead). KF, Kaplan fiber insertion; LE, lateral epicondyle (after removal of the lateral collateral ligament).

Figure 6.

Reflection of the superficial iliotibial band (sITB) and its deep layers reveals the anterolateral joint capsule with a thickening (mid-third capsular ligament; area between the 2 dotted lines) anterior to the lateral collateral ligament (LCL). This mid-third capsular ligament was observed in 35% of the specimens.

Figure 7.

Removal of the anterolateral capsule revealed the coronary ligament, consisting of the meniscofemoral (*) and meniscotibial (**) ligaments. Medial to the coronary ligament, the inferior genicular artery (white arrowhead) runs from posterior to anterior.