Medial approach to the knee joint

The medial approach to the knee joint provides excellent exposure of the ligamentous structures on the inner side of the knee.

Indications for the Medial Approach to the Knee Joint

1. Repair of the medial knee ligaments.
2. Repair or meniscectomy for a medial meniscus tear.
3. Repair for an anterior cruciate ligament injury.

Patient Positioning

• Place the patient supine on the operating table.
• Flex the affected knee to approximately 60°, abduct the hip on the same side, and externally rotate it, resting the foot on the opposite shin.

Landmarks and Incision

• Landmark: The adductor tubercle along the medial side of the knee.
• Incision: Make a long, curved incision starting at a point 2 cm proximal to the adductor tubercle of the femur. Curve it anteriorly and distally to a point 6 cm below the joint line on the anteromedial aspect of the tibia. The center of this incision runs parallel to the medial border of the patella, approximately 3 cm medial to it.

Internervous Plane

• There is no true internervous plane in the medial approach to the knee, as the nerves run posteriorly in the popliteal fossa at the level of the knee, making the dissection relatively safe.
• The only cutaneous nerve at risk is the saphenous nerve and its branches.

Superficial Dissection

• Raise the skin flaps to expose the fascia.
• The exposure should extend from the midline anteriorly to the posteromedial corner of the knee posteriorly.

The infrapatellar branch of the saphenous nerve crosses the operative field transversely and is sacrificed. However, the saphenous nerve itself, which emerges between the gracilis and sartorius muscles, must be preserved, along with the long saphenous vein in the posteromedial part of the dissection.
(The infrapatellar branch of the saphenous nerve should be divided and its end buried in fat to reduce the likelihood of forming a painful neuroma.)

Deep Dissection

To expose the deep structures of the knee, the layers covering them must be incised either in front of or behind the superficial medial collateral ligament (the medial collateral ligament).

These separate incisions allow access to the anterior and posterior parts of the medial side of the joint, respectively.

1. In Front of the Superficial Medial Ligament

Use the anterior approach to expose the superficial medial ligament, the anterior part of the medial meniscus, and the cruciate ligament.

• Incise the fascia along the anterior border of the sartorius muscle, following its fibers, starting from its attachment on the subcutaneous surface of the tibia and extending proximally to a point 5 cm above the joint line.
• The anterior border of the sartorius is difficult to define at the knee joint level, so it should be located either at the tibial attachment of the muscle or at the proximal end of the wound.
• Now flex the knee further to allow the sartorius muscle to retract posteriorly, exposing the other two components of the pes anserinus: the semitendinosus and gracilis muscles, which lie beneath and behind the sartorius.
• Retract all three muscles posteriorly to expose the tibial attachment of the superficial medial ligament, which lies deep and distal to the anterior border of the sartorius. Note that the ligament attaches approximately 6 to 7 cm below the joint line, not near it.
• Apply gentle traction to the superficial medial ligament to expose the injury site. Alternatively, apply strong valgus force to the knee to visualize the site of the ligament rupture.
• Make a medial parapatellar longitudinal incision to gain access to the inner aspect of the anterior compartment of the joint.
• To avoid damaging the underlying medial meniscus, begin the incision well above the joint line and cut carefully.

2. Behind the Superficial Medial Ligament

The posterior approach exposes the posterior third of the meniscus and the posteromedial corner of the knee.

• Incise the fascia along the anterior border of the sartorius muscle in the same manner as for the anterior approach.
• Retract the sartorius muscle posteriorly, together with the semitendinosus and gracilis muscles.
• If the posteromedial joint capsule is damaged, the back of the medial femoral condyle is usually visible, with the underlying meniscus visible through the torn capsule.
• If the capsule is intact, expose the posteromedial corner of the joint by separating the medial head of the gastrocnemius muscle from the semimembranosus muscle. Although both muscles are supplied by the tibial nerve, this intermuscular plane is a safe area for dissection, as the semimembranosus receives its nerve supply far proximal to its attachment and the gastrocnemius receives it far distally.
• Finally, separate the medial head of the gastrocnemius from the posterior capsule of the knee joint by blunt dissection, extending almost to the midline.
• Once fully exposed, the posteromedial corner of the capsule can be examined for damage.
• A second arthrotomy behind the superficial medial ligament (the tibial collateral ligament) allows for examination or treatment of posterior intra-articular or periarticular pathologies. Repair of the posteromedial corner of the joint is also possible.

Extension of the Approach

• The medial approach to the knee joint cannot be usefully extended in any direction.

Dangers

Structures at risk during the medial approach to the knee joint include:

1. Infrapatellar branch of the saphenous nerve: It runs transversely across the operative field, is usually sacrificed, and should be buried in fat to prevent neuromas.
2. Long saphenous vein: It is located between the sartorius and gracilis muscles.
3. Medial inferior genicular artery: It can be damaged when the medial head of the gastrocnemius is lifted from the tibia.
4. Popliteal artery: It lies along the midline of the posterior joint capsule adjacent to the medial head of the gastrocnemius.

References

• Book "Surgical Exposures in Orthopaedics" – 4th Edition