The ligament complex connecting the outer aspect of the leg bone (tibia) to the thigh bone (femur) consists of a number of structures (please see Knee Anatomy & Function). These structures are collectively known as the Posterolateral Complex (PLC). They prevent the tibia from moving excessively outward (laterally) beneath the femur.

The importance of the PLC has been recently appreciated. PLC injuries seldom occur alone. They are generally associated with an ACL or PCL injury. They are thus quite often missed. Patients who simply undergo an ACL or PCL reconstruction with a missed or untreated PLC have a significant failure rate whereby after some years the reconstructed ligament might stretch and the knee becomes painful and possibly slightly deformed.

PLC injuries occur when the leg bone (tibia) is thrust forcefully inwards as a result of a direct blow, road traffic accident or sporting injury. Associated cruciate ligament injuries might contribute to instability in more than one direction. A careful expert clinical examination generally provides a good clue. Stress X rays and MRI scans can provide additional information.
Minor strains can be managed with immobilization in a brace for 2-3 weeks followed by gradual supervised mobilization and strengthening of the joint.
However, the more common severe tears and tears associated with other ligament injuries cause an opening up of and consequent instability of the joint when the leg bone is thrust inwards. These tears need to be reconstructed in the first 3 weeks post injury preferably between 10-14 days, alongwith other ligament reconstructions. Rehabilitation differs if the PLC is reconstructed.

Quite often PLC injuries are missed. After several months or years of a cruciate (ACL or PCL) reconstruction, patients may complain of
  • Subjective Instability
  • inability to run, feeling of giving way
  • Pain on the inner side of the knee
  • Mild, progressive deformity whereby the tibia drifts towards the inside (a varus deformity) Such symptoms arise because of an insufficient PLC. These patients might require additional procedures to a PLC reconstruction which might include a
  • Joint Realignment Surgery
  • Revision ACL or PCL reconstruction
Recognition and Management of PLC injuries, though a recent art (and thus best treated by Knee Specialists ) is significantly important in providing a good result – a stable painless knee.