Orthopaedic surgical approaches 2022, Nov, 21 | 12:00 am

Applied Surgical Anatomy of the Lateral Side of the Knee

Applied Surgical Anatomy of the Lateral Side of the Knee‌

 

 

Overview

 

The supporting structures on the lateral side of the knee fall into three layers. Because the anatomy can be distorted in pathologic states, a clear

understanding of the normal anatomy is required before explorations19 are carried out.

Outer Layer

The outer layer is continuous with the deep fascia of the thigh (see Fig. 10-49). The iliotibial band, the aponeurotic tendon of the tensor fasciae latae and gluteus maximus muscles, is a thickening in the deep fascia of the thigh. Its fibers run longitudinally.

The band inserts into a smooth facet on the anterior surface of the lateral condyle of the tibia that is known as Gerdy tubercle. It also sends fibers into the deep fascia of the leg and reinforces the lateral patellar retinaculum. In injuries to the knee involving severe varus stress, its insertion may be avulsed. When the knee is in extension, the iliotibial band is anterior to the axis of rotation and maintains extension. With the knee flexed to 90 degrees, it moves behind the axis of rotation and can act as a flexor. This variable relationship to the axis of rotation may be a feature in the genesis of the pivot shift test for a torn anterior cruciate ligament.20

 

 

 

Figure 10-49 A slightly anterolateral view of the outer layer of the knee. The lateral patellar retinaculum, the biceps femoris, and the iliotibial band constitute the outer layer.

 

The biceps femoris muscle, a part of the outer layer, is enclosed by the deep fascia, as is the sartorius muscle on the medial side.

The lateral patellar retinaculum is a tough structure derived largely from the fascia covering the vastus lateralis muscle.

Middle Layer

The superficial lateral ligament (fibular collateral ligament) runs from the lateral epicondyle of the femur to the head of the fibula. The lateral inferior genicular vessels run between the ligament and the joint capsule itself. Because the ligament is attached to the femoral condyle behind the axis of rotation, it is tight in extension. When the ligament is damaged, subsequent functional problems are minimized by the existence of other

supporting structures on the lateral side of the knee, especially the iliotibial band (Fig. 10-50).

A second supporting structure of the lateral side of the knee has recently been described—the anterolateral ligament of the knee.21

This structure passes anterodistally from an attachment proximal and posterior to the lateral femoral epicondyle to the margin of the lateral tibial plateau, approximately midway between Gerdy tubercle and the head of the fibula. The ligament is superficial to the lateral (fibular) collateral ligament proximally, from which it is distinct, and separate from the capsule of the knee.

 

 

 

Figure 10-50 The lateral patellar retinaculum, the iliotibial band, and the deep

fascia (outer layer) have been excised to reveal the superficial lateral ligament (middle layer) and the joint capsule (deep layer). Note that the lateral inferior genicular artery runs along the joint line between the middle and deep layers.

 

Deep Layer

The deep layer consists of the true capsule of the knee joint, the fibrous tissue attached just above and below the articular surfaces of the knee. Two other structures run with the capsule:

  1. The popliteus muscle originates from the popliteal surface of the tibia above the soleal line. Its tendon, which lies within the joint capsule, attaches to the lateral condyle of the femur and the posterior aspect of the lateral meniscus.

  2. The short lateral ligament (deep lateral ligament) is a thickening in the true capsule of the knee. The ligament is developed poorly; it runs underneath the superficial lateral ligament (fibular collateral ligament), from the lateral femoral condyle to the head of the fibula. Unlike the medial ligament, the lateral ligament does not attach to the meniscus. That is why the lateral meniscus can move far more freely than can its medial counterpart (Fig. 10-51).

 

 

Figure 10-51 A true lateral view of the knee joint. The biceps femoris, iliotibial band, and vastus lateralis have been excised to reveal the deeper layers. The joint capsule has been excised anterior and posterior to the superficial lateral ligament (fibular collateral ligament) to expose the intra-articular structures, notably the popliteus tendon and the lateral meniscus.

 

Landmarks and Incision

 

Oblique or longitudinal skin incisions cross the relaxed skin tension lines almost perpendicularly and may result in broad scars.

 

Superficial and Deep Dissections

  1. Approach for lateral meniscectomy

    1. Incise the superficial and deep layers, cutting the lateral patellar retinaculum (see Fig. 10-50).

    2. The true capsule of the joint is very thin at this point. Incise it with its synovium to gain access to the joint surface.

  2. Lateral exposure of the knee and its supporting structures

    1. Open the superficial layer in the plane between the biceps femoris muscle and the iliotibial band (see Fig. 10-50).

    2. Incise the joint either in front of or behind the superficial lateral ligament, the middle layer of the lateral side (see Fig. 10-51).

    3. Incise the capsule of the joint (the deep layer) in front of or behind the superficial lateral ligament. Do not damage the tendon of the popliteus muscle, which lies between the outer border of the lateral meniscus and the capsule of the joint (see Fig. 10-51).