Superficial part of tibial collateral ligament

At a glance

English

Superficial part of tibial collateral ligament

Latin (TA2)

Pars superficialis ligamenti collateralis tibialis

System

Ligament

Region

Lower limb

Side

Paired, left and right

About the superficial part of tibial collateral ligament

The superficial part is the long outer layer of the tibial (medial) collateral ligament, the main ligament on the inner side of the knee. It is a broad, flat band set slightly towards the back of the medial side of the joint, and it lies over the shorter deep part, with a small bursa between the two layers.

Above, it is fixed to the femur's medial epicondyle, just below and in front of the adductor tubercle. Below, its long anterior fibres descend and lean slightly forwards to a broad attachment on the medial surface of the tibial shaft, several centimetres below the joint line. Its shorter posterior fibres slope backwards as they go down and reach the tibia just above the semimembranosus groove; this posterior portion is often called the posterior oblique ligament. Over its lower part pass the united tendons of sartorius, gracilis and semitendinosus, the pes anserinus, with the anserine bursa between tendon and ligament.

Deep to the ligament run the inferior medial genicular nerve and vessels, along with the front of the semimembranosus tendon, to which it is linked by a few fibres. Its main function is to resist valgus force, the inward push that would open the medial joint and give a knock-kneed angulation, and it also limits external rotation of the tibia. It is tightest when the knee is straight. Like the deep part, it is thought to represent the old lower tendon of adductor magnus.

This is the knee ligament most often sprained. Injury follows a valgus force on a slightly flexed knee, as in skiing, contact sports or breaststroke kicking, or a blow to the outside of the knee. The valgus stress test at about 30 degrees of flexion assesses it. Sprains are graded from minor stretching to complete tear; even many complete tears heal well in a hinged brace, and surgery is kept for persistent instability or combined injuries.

Attachments and function

Attaches from

The femoral medial epicondyle, just below the adductor tubercle.

Attaches to

The medial surface of the tibial shaft below the condyle, deep to the pes anserinus, with posterior fibres to the tibia above the semimembranosus groove.

Function

The main restraint against valgus force on the knee; also limits external rotation of the tibia, tightest in extension.

Nerve supply

Articular branches of the saphenous and obturator nerves; the inferior medial genicular nerve runs deep to it.

Blood supply

The superior and inferior medial genicular arteries.