This infomation is designed to explain the anatomy and function of the posterolateral complex (PLC), what can happen as a result of injury, a description of the surgery to reconstruct these structures and the rehabilitation thereafter.
Most but not all reconstructions of the PLC are performed in association with reconstruction of another of the knee ligaments. If this is the case please also refer to the information sheet relating to the other ligament(s) as well.
Anatomy of the Posterolateral Complex
The posterolateral compartment of the knee is a complex arrangement of ligaments, joint capsule and muscles. This arrangement acts as both a static and a dynamic stabilizer of the knee, controlling outward rotational movement backwards of the tibia (shin) on the femur (thigh). This movement can be imagined with the knee bent, keeping your thigh still and turning your foot outwards.
Posterolateral Complex Injury
Although PLC injury is uncommon, it is often associated with other ligament damage in the knee, such as the cruciate ligaments. The mechanism of injury is often the knee pushed back on itself with the lower leg turned out or a direct blow. As a result of injury the knee may become extremely unstable giving way on twisting or pivoting activities. There may be an altered walking pattern such as the foot turned outwards, the knee slightly flexed or a ‘thrust’ of the knee as you walk.
Posterolateral Complex Reconstruction
If you are undergoing a PLC reconstruction in conjunction with other ligament reconstruction please read the relevant information sheet which gives more full details about your proposed operation. However the description given below is usually indicative of what a PLC reconstruction entails.
There are two principal choices for the graft used to reconstruct the PLC. If possible, it is probably best to use the hamstring tendons from either the leg which is undergoing the surgery or alternatively the hamstrings from the other leg if the first set is needed for another ligament to be reconstructed (e.g. the anterior or posterior cruciate ligaments). The grafts when taken from the patient’s own body are referred to as autograft. However not enough graft may be available or the hamstrings may be unsuitable, and in these circumstances the graft is taken from another person – this is termed allograft.
There are advantages and disadvantages of both autograft and allograft but most surgeons would agree that if possible it is best to use autograft. Autograft is safe in that it is free from the risk of infection and has the least chance of “rejection” – it is also cheap! However its supply is limited and there can be some consequences in the short and longer term from taking the graft. Allograft has the advantage of a plentiful supply but has the disadvantages of possible risks of infection, increased graft “rejection” and expense.
The choice of graft will be discussed with you in detail with your Consultant and please feel free to ask any questions at any stage about this topic, which understandably may be very important to you.
The operation itself of PLC reconstruction involves an incision on the outer aspect of the knee. The operation strictly speaking is not in the knee but on the outside of the joint. If the hamstring tendons are used, there will also be a small incision on the inner aspect of the knee, from where they are harvested.
The graft, of whatever type, is placed through the head of the fibula (the smaller of the two bones of the leg) and secured in the outer aspect of the femur using a screw device.
As it is likely that you are having a PLC reconstruction in conjunction with a cruciate ligament reconstruction, the PLC reconstruction will alter the operative protocol of the cruciate ligament reconstruction as stated in the patient information leaflet relating to that particular operation.
PLC plus Anterior Cruciate Ligament (ACL) Reconstruction
Your knee will be placed in a back splint for two weeks restricting all movement. At two weeks a brace is fitted allowing a full range of movement. You will usually be requested to remain in this brace for 6 weeks after surgery.
You will need to be non–weight bearing during this first six weeks i.e. you will need to avoid putting any weight through your operated leg. The new PLC ligament can be damaged or stretched if excessive strain is placed on it in this early phase.
On removal of the brace at 6 weeks you can then follow the normal post–operative protocol for the ACL reconstruction.
PLC plus Posterior Cruciate Ligament (PCL) Reconstruction
Your knee will be placed in a back splint for two weeks restricting all movement. At two weeks a PCL brace, specifically used for rehabilitation for this type of reconstructive surgery, is fitted allowing full extension (straightening) and flexion (bending) to 900. You will usually be requested to remain in this brace for 6 weeks after surgery.
You will need to be non–weight bearing for 6 weeks i.e. during this time you should not put any weight through your operated leg as this may damage the new PLC ligament.
To protect the posterior cruciate ligament graft (not the PLC) you will need to avoid actively flexing (bending) your knee for 6 weeks as active contraction of the hamstring muscles may harm the graft by placing it under too much strain.
On removal of the brace at 6 weeks you can then follow the normal post–operative protocol for PCL reconstruction.
Complications of Posterolateral Complex reconstruction
Possible risks and complications
There is no surgical procedure that is free from complications. Ligament reconstruction, especially recently, has a very good record of safety and success, but complications can occur. Such complications can include;
- Stiffness of the knee. The knee may have difficulty gaining full extension or flexion. This is minimised by early physiotherapy and in addition a great deal of effort on the part of the patient. Sometimes it may be necessary to manipulate the knee under anaesthetic or carry out an arthroscopy to break down adhesions if the knee does become stiff.
- Persistent pain over the front of the knee. There may be persistent numbness on the inner aspect of the leg, or the front of the leg, and rarely an area develops tiny ‘shocks’ when lightly touched.
- Persistent swelling of the knee.
- Deep venous thrombosis (DVT) or ‘blood clots in the veins’. Every attempt is made to minimise this complication, although heparin is not given routinely. Unless the procedure is an emergency, patients should not be taking the oral contraceptive pill for 6 weeks prior to surgery. Finish your current pack and take other contraceptive precautions until after your operation. It is also advisable not to be taking HRT at the time of surgery. Please ask for advice if necessary.
- Infection of the knee. This is a rare but extremely serious complication. Antibiotics are given during and shortly after the operation to minimise the risk.
- Failure of the graft. The knee may start to give way again. This may occur within a short time of operation or after a considerable period. The 5 year success rate in preventing instability is approximately 90% (this figure has increased considerably in recent years).
The risks and complications for PLC reconstruction are essentially the same as those mentioned above. However there is one added risk with this procedure;
- Peroneal nerve palsy – there is a small but recognised risk to the nerve which controls the muscle action of pulling the foot upwards i.e. lifting the foot and toes as you walk. At surgery the nerve is identified and protected and should not be cut; however formation of a large bruise (haematoma) around the area of the nerve may result in altered function of this nerve. If this bruising does occur, the function of the nerve usually returns but this may take several months. On very rare occasions this does not return and thus this can be a profound complication, which although rare needs to be appreciated.
Please contact the hospital at which you underwent surgery if you are at all concerned that there is a problem. In particular, act immediately if you develop a fever, severe pain or significant wound problems. If you develop a problem after your surgery you do not need to contact your GP (unless you wish to do so); please telephone your Consultant, or if it is outside of office hours please contact the hospital in which you had your surgery and they will be able to contact him for you.
You will have been recommended surgery only if the potential benefits of the operation outweigh the risks. If you have any specific questions relating to your surgery or rehabilitation please contact your Consultant or physiotherapist.
Derek Bickerstaff MD FRCS FRCSED
Consultant Orthopaedic Surgeon