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The basics

 

  • The PCL is the ligament at the back of the middle of the knee that prevents the tibia (shin bone) from wobbling too far backwards.
  • PCL tears are much less common than ACL tears.
  • PCL tears tend to occur from injuries such as falling onto the front of a bent knee, from hyperflexion (too much deep sudden bending) of the knee or from dashboard-type injuries (where the knee is driven forwards into the front of the dashboard in a car crash).
  • Whereas with ACLs, where most tears are complete tears, with PCL injuries the tears is often only partial.
  • When the ACL tears, patients have severe pain and marked rapid swelling of the knee, with difficulty weight bearing. When the PCL is injured, however, the symptoms are quite often somewhat less severe, with vague ill-defined pain in (or behind) the knee, and only moderate swelling.
  • The most common thing that happens to a PCL tear is that initially the injury is missed, and it is often only picked up on at a much later stage when patients present with secondary damage in the knee, such as meniscal tears or degenerative changes.
  • Most isolated PCL tears respond very well to conservative (non-surgical) treatment, specifically with intensive targeting physiotherapy. If a patient is able to sufficiently strengthen their quads and speed up their reflexes (proprioception) then they may well be able to compensate for the increased laxity in their knee and end up with a functionally stable joint.
  • If a patient does well enough with physio rehab then they will not need a surgical PCL reconstruction.
  • If a patient has a complete tear of their PCL and if they suffer significant ongoing problems despite a full and proper attempt at physio rehab, then they might end up requiring a surgical PCL reconstruction.
  • If other ligaments in the knee are also torn at the same time as a PCL tear (i.e. a multi-ligament injury) then patients tend to do badly without surgery, and surgical reconstruction of all of the torn ligaments at the same time normally ends up being required.
  • With a PCL reconstruction, narrow tunnels are drilled through the tibia (shin bone) and the femur (thigh bone), a new ligament is created by taking a tendon (from elsewhere in the patient themselves, = an autograft, or from a donor, = an allograft), and this is threaded through the knee. The ligament is fixed at the top, tensioned and then fixed under tension at the bottom, to give a new tight ligament inside the knee. With time, blood vessels grow into the tendon graft and seed it with the patient’s own living cells, and the graft becomes a living functioning part of the patient’s own knee
  • The rehab after PCL reconstruction is slow. Patients are normally kept in a knee brace and with crutches for the 1st 6weeks. Regular intensive physio sessions are required. Return to sport is not allowed until a full 9 months post-op.

 


 

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The posterior cruciate ligament is the main ligament at the back of the knee, connecting the femur and the tibia and preventing the tibia from wobbling too far backwards (posteriorly). The PCL is bigger than the ACL, and is not as commonly injured. The most common mechanisms of injury for a PCL tear are either a dashboard-type injury or a fall onto the front of the shin (where the shin is forced backwards) or a hyperflexion injury, which tends to happen when someone falls onto their knee and the knee is forced suddenly into deep flexion. PCL injuries can also occur with hyperextension of the knee or from major twisting injuries, and PCL tears are often found in combination with tears of other of the knee ligaments in more major injuries, such as the ACL and/or the posterolateral corner structures.

The most common thing that happens with a PCL injury is that the diagnosis is actually missed! (or at the very least delayed). After a PCL injury there is pain and swelling in the knee, but this is not as severe, overt or long-lasting as it can be with injuries of the ACL (which are far more common), and PCL deficiency tends often to cause less severe ongoing problems in a knee. There may be wobbliness and instability, especially with impact/twisting manoeuvres. Alternatively, the knee might just not feel ‘right’. Also, PCL deficiency if left untreated often ends up resulting in the patient developing further additional damage in the knee with time, such as meniscal tears.

 

CLICK HERE  for further information about PCL tears


Most patients with an isolated PCL tear actually do very well with intensive focused physiotherapy rehab, centering on building up as much strength and as fast reflexes as possible in the quads muscles, to try and compensate for the ligament deficiency. The following are indications for proceeding with surgical PCL reconstruction:-

  • If a patient with no PCL has tried appropriate physiotherapy rehab, but they are still suffering significant ongoing instability of the knee.
  • If the injury is a multi-ligament injury (i.e. combined with an ACL and/or posterolateral corner injury), as these rarely ever do well without surgical reconstruction of all the damaged ligaments together.
  • If, as a result of the PCL deficiency and any instability in the joint the patient is developing progressive damage to the joint, such as meniscal tears.
  • If the patient also needs other reconstructive procedures in the joint, such as meniscal replacement surgery (e.g. meniscal transplantation), which can only be undertaken in a solid stable joint.

Reconstruction of the PCL is a similar procedure to ACL reconstruction, but the surgery is somewhat more complex and difficult, and the early rehab somewhat slower.

When a PCL tears, the damaged ligament tissue is often frayed and tends to scar up and shrink back, and direct primary repair is very rarely ever feasible or appropriate. Instead, the ligament has to be replaced with a new ligament, called a graft. Under an anaesthetic, bone tunnels are drilled from the femur and the tibia either side of the knee, passing into the middle of the joint. The graft is passed along these tunnels, fixed at one end, tensioned, and then fixed under tension at the other end. At the same time, a knee arthroscopy is performed and any other concomitant damage in the knee is sorted out.

As with ACL reconstruction, there are various options available for where to obtain a graft from and what type of graft to use. Unlike ACLs, however, the patellar tendon graft is not a viable option, and the main choice is between a hamstring autograft or an allograft.

 

CLICK HERE  for further information about graft options




Recovery and rehab


Most patients are able to be discharged from hospital the morning of the following day, fully weight bearing but with crutches initially, for comfort and support. Unlike a straight forward ACL reconstruction, we normally put patients into a hinged knee brace for the first 6 weeks after a PCL reconstruction, as the graft tends to need somewhat more careful protection than an ACL graft.

The first week or so after surgery is spent pottering around at home and taking things easy. After that, patients start regular intensive physiotherapy rehab treatments, to get the movement, strength and reflexes back in the knee. Most patients are able to restart gentle slow jogging on a treadmill by 3 months post-op, with a return to sport at 9 months.




Results


The results of PCL reconstruction are good, with a success rate (based on patient symptoms, function and overall satisfaction) of about 90%, but this does very much depend on what other potential damage there might be in the joint and what other concomitant procedures might have needed to be undertaken at the same time as the PCL reconstruction (as the initial presentation of patients with a PCL tear to a knee surgeon is so often delayed, and hence by the time that a patient actually gets their PCL reconstruction there are by then already other issues with the joint that have sadly developed).





Written by Mr Ian McDermott
Consultant Knee Surgeon London
Last updated 24-6-15