Knee joint has complex structure and function. This is supported by four ligaments which prevent the subluxation of the knee joint in all directions. The most commonly injured of these remain the Anterior cruciate ligament which prevents the anterior subluxation and provides rotational stability to the knee joint.

Posterior cruciate ligament acts as a central stabilizer and prevents posterior subluxation of the knee. The patients cheifly complains of climbing downstairs & pain on deep flexion. The patient does not usually complain of instability in these cases.

The inner side(medial) of the knee is supported by the Medial collateral ligament which prevents opening of the knee from inside when a thrust from outwards in is applied. The ligament also has a role in upto 30 degrees of knee bending. Usual cases complain of severe pain at the inside of the knee accompanied with instability. Mostly this heals with rest and conservative treatment. A small subset of patients may have to undergo a surgical treatment for the same.

Similarly the ligamentous complex preventing opening up of the knee towards outside with application of a thrust from inside out is called the Posterior-lateral complex or the PLC. This prevents both pivoting and lateral opening of the joint.

These are essential for providing stabillity to the knee and any one of these if compromised may lead to a change i the normal kinematics of weight bearing. In long term, meniscal damage and cartilage erosions become common and lead to poor painful prognosis.

The procedure followed for these is reconstruction of a new ligament using graft from same or opposite side as per patient demand and expectations.