Lateral access to the knee joint

Introduction

The lateral approach to the knee joint provides access to all supporting structures on the outer side of the knee.

This approach can be used for:

1. Exposure for repair or reconstruction of the lateral knee ligament.
2. Open repair of a lateral meniscus tear.

Patient Positioning

Place the patient supine on the operating table with a sandbag under the buttock on the affected side. This position internally rotates the leg, providing better exposure of the outer knee. Flex the knee to 90 degrees.

Landmarks and Incision

Landmarks

• Lateral border of the patella.
• Gerdy’s tubercle, the insertion point of the iliotibial tract.

Incision

• A long, curved incision is necessary to adequately expose all lateral knee structures.
• Begin the incision at the level of the mid-patella, 3 cm lateral to it.
• With the knee still bent, extend the incision downward, crossing Gerdy’s tubercle on the tibia, and continue 4 to 5 cm distal to the joint line.
• Complete the incision by curving the upper end to follow the line of the femur.

Internervous Plane

The internervous plane for the lateral approach to the knee lies between:

1. Iliotibial tract (ITB): This is the fascial aponeurosis of two muscles, the gluteus maximus and the tensor fasciae latae, both supplied by the superior gluteal nerve.
2. Biceps femoris tendon: This is innervated by the sciatic nerve.

Although the iliotibial tract itself has no nerve supply, the plane between it and the biceps femoris muscle can be considered an internervous plane due to the muscular origin of the biceps femoris.

Superficial Dissection

• Mobilize the skin flaps widely. Beneath them, two main structures are found: the iliotibial tract, which runs downward to attach to the anterior border of the tibia and Gerdy’s tubercle, and the biceps femoris muscle, which runs downward and forward to insert on the fibular head. Both structures can be avulsed from their attachments under high stress on the knee.
• Incise the fascia in the interval between the iliotibial tract and the biceps femoris muscle, taking care to avoid the common peroneal nerve located at the posterior border of the biceps tendon.
• Retract the iliotibial tract anteriorly and the biceps femoris muscle (with the peroneal nerve) posteriorly to expose the superficial lateral ligament (fibular collateral ligament), which runs from the lateral femoral epicondyle to the fibular head. The posterolateral corner of the knee capsule is also visible.

Deep Dissection

Joint entry is achieved either anterior or posterior to the superficial collateral ligament.

Anterior Arthrotomy

• To examine the entire lateral meniscus, incise the capsule anterior to the ligament.
• Perform a separate fascial incision to create a lateral parapatellar approach.
• To avoid cutting into the meniscus, start the arthrotomy 2 cm above the joint line.

Posterior Arthrotomy

• To examine the posterior horn of the lateral meniscus, identify the lateral head of the gastrocnemius muscle at its origin on the posterior aspect of the lateral femoral condyle.
• Dissection proceeds between this area and the posterolateral corner of the joint capsule. The lateral superior genicular artery (or arteries) lie in this region and must be ligated or coagulated.
• In trauma cases, dissection in this area may already be complete. Make a longitudinal incision in the capsule, starting the arthrotomy well above the joint line to avoid injuring the meniscus or the popliteus tendon.
• An arthrotomy of the posterior half of the joint capsule must be performed carefully to avoid injury to the popliteus tendon, which lies outside the meniscus.
• This arthrotomy allows inspection of the posterior half of the lateral compartment behind the superficial lateral ligament.

Extension of the Approach

The lateral approach to the knee cannot be usefully extended.

Dangers

Structures at risk during the lateral approach to the knee include:

1. Common peroneal nerve: At risk at the posterior border of the biceps femoris muscle.
2. Popliteal artery: At risk behind the posterior horn of the lateral meniscus.
3. Popliteus tendon: Runs intra-articularly next to the lateral meniscus and attaches to the posterior aspect of the meniscus and femur. It is at risk during a posterior arthrotomy.
4. Lateral superior genicular artery: At risk between the femur and vastus lateralis.
5. Lateral inferior genicular artery: At risk between the lateral head of the gastrocnemius and the posterolateral corner; should be ligated.

References

• Surgical Exposures in Orthopaedics – 4th edition
• Campbell’s Operative Orthopaedics, 12th edition