THE POSTERIOR CRUCIATE LIGAMENT (PCL)
The knee is formed by the thigh bone (femur) and leg bone (tibia). These bones are joined by four primary ligaments, one on each side (the collaterals), one in the front (the ACL) and one at the back, the posterior cruciate ligament (PCL).
The PCL restrains the tibia from moving excessively backwards under the femur.
Being a very strong ligament, injuries to the PCL are relatively uncommon. A backward directed excessive force on the front of the upper part of the tibia (such as a dashboard injury whilst sitting in the car or a player falling very hard on the front of his knee) can lead to a PCL injury. Quite commonly, dislocated knees following a high velocity road traffic accident are found to have PCL tears.
As it is the strongest of the abovementioned 4 ligaments, an injury to the PCL is often associated with other ligament injuries. A careful evaluation is thus mandatory.
Injuries to the PCL could be:
A partial tear (only some fibres are torn)
An avulsion (i.e. rip off with a piece of bone) from the back of the tibia
A complete tear within its midsubstance
Partial tears have a good chance of healing without surgery. Surgical intervention is generally required in avulsions and complete tears especially when complete tears are associated with other ligament injuries.
The diagnosis of an PCL injury is usually arrived at by determining the mechanism of injury, examining the knee, determining the presence or absence of blood within the joint, and performing diagnostic studies. These may include x-rays, MRI scans and stress tests of the ligament.
The initial treatment of an acute PCL injury (with the exception of a PCL avulsion) often includes ice, anti-inflammatory medication, and physical therapy which is directed at restoring the range of motion of the injured knee and retaining its strength. Once the inflamed knee settles (it typically takes 10 -14 days), it is examined for instability. One or more ligaments might be involved. Thus an accurate assessment is essential for a good outcome.
PCL avulsions must be operated early whereby the bone fragment is reattached to its original site retaining the normal tension of the ligament.
NON SURGICAL MANAGEMENT
Partial tears or the rare isolated PCL tears can be given a trial of conservative treatment for six weeks. This involves resting the knee in a special brace (with a tibial lift off i.e. pushing the tibia forward at all times), and intermittent ice therapy with anti-inflammatory medication.
Gradual supervised physical therapy which is best done by a Specialist Physiotherapist would involve initial selective muscle strengthening, gradual range of motion with a forward force on the tibia maintained and weightbearing (walking) after at least 3-4 weeks. Thus, a structured physical therapy programme is essential for success.
PCL avulsion injuries require immediate surgery. This is treated as a fracture whereby the avulsed bone is reattached to the tibia retaining ligament tension. Isolated complete tears which have not healed despite a trial of conservative treatment or complete tears associated with other ligament tears in the same knee require surgical intervention. This is best done at least 10-14 days after the injury.
Recently evolved techniques allow us to carry out these procedures arthroscopically. Arthroscopic surgery has its inherent advantages of less tissue trauma, more accurate reconstructions, and quicker rehabilitation. This requires advanced arthroscopic skills. Conventional methods involved large incisions at the back of the knee.
WHAT TO EXPECT
Patients with ligament injuries are usually young without any associated medical ailments. They are thus admitted the morning of surgery (after fasting for approximately 6 hours). Following some preliminary tests from an anaesthetic point of view, they undergo the procedure under a combined spinal and epidural anaesthesia.
Medicines through the epidural catheter provide a painfree experience during and after surgery.
Incisions are minimal (from where the graft is taken) and the entire procedure is done arthroscopically through two or three small holes. The procedure takes about 45 minutes.
Following surgery, the knee is kept in a special splint which has a tibial lift off. This is a small sponge or foam beneath the upper tibia which keeps the tibia forward at all times. This position helps relieve tension on the reconstructed PCL, thereby helping it heal.
Contrary to the ACL rehabilitation protocol, the knee is rested for approximately 3 weeks. During this phase, the patient is encouraged to do certain exercises which naturally help bring the tibia forward and strengthen muscles which would help the patient walk later. Gradual range of motion exercises are started in a structured fashion at 3 weeks. Combined reconstructions require even more careful supervision by Specialist Physiotherapists.
Patients are discharged the next day. A well structured rehabilitation protocol by experienced physiotherapists has benefited a large number of patients at our clincs. Generally achieved targets from this protocol are: