Patient Education · Knee

PCL Reconstruction

The ACL's less famous partner. Torn a different way, treated differently — and the recovery asks more patience than any other ligament in the knee.

Dr. Darin W. Allred Darin W. Allred, MD Board-certified orthopedic surgery & sports medicine
~1 hrTypical time for the operation
4 monthsHow long the brace stays on
Often noneMany PCL tears are treated without surgery
6–9 moBack to sport

What the PCL does

Two ligaments cross in the middle of your knee. The ACL stops your shin bone sliding forward. The PCL — the posterior cruciate ligament — stops it sliding backward. It is the thicker and stronger of the two.

How it tears

The mechanism is different from an ACL tear, and knowing it helps explain everything that follows. The PCL tears when something drives the top of the shin bone backward:

  • A dashboard injury — a car wreck where the bent knee strikes the dash.
  • A fall onto a bent knee with the foot pointed down. This one happens on ranches, on stairs, and on sports fields.
  • A hyperextension or a hard blow to the front of the shin.
Illustration of a bent knee showing the cruciate ligaments
With the knee bent, gravity pulls the shin bone backward - exactly the direction the PCL resists, and the reason the brace stays locked straight.

PCL tears are also easy to miss. There is often no dramatic pop, less swelling than an ACL tear, and people walk on it. Many are found weeks or months later when someone notices a vague ache and trouble going down stairs or slopes.

Why many PCL tears do not need surgery

Unlike the ACL, an isolated PCL tear often does well without an operation. The PCL has a better blood supply and can heal to a functional length, and the quadriceps can compensate for a great deal of what it does — because the quad actively pulls the shin forward, which is exactly the direction a torn PCL fails to control.

So for an isolated tear, my first line is a proper rehabilitation program built around quadriceps strength, often in a brace. Plenty of people return to full activity that way. I would rather build your quad than reconstruct your ligament if the quad will do the job.

When I do reconstruct it

  • A severe tear with the shin bone sagging significantly backward on examination.
  • More than one ligament torn. This is the big one — a PCL tear alongside a corner or collateral ligament injury behaves completely differently and usually needs surgery.
  • Instability that persists despite a genuine rehabilitation effort.
  • A bony avulsion, where the ligament pulled a fragment of bone off. That piece can often be fixed back down, and it heals well.

There is a long-term argument too: a knee left with a slack PCL loads the kneecap and the inner compartment abnormally, and arthritis there is a recognized consequence years later.

What the operation does

Like the ACL, we reconstruct rather than repair. A graft is passed through tunnels drilled in the thigh bone and shin bone along the ligament's path and fixed at both ends.

Illustration of the knee from the side showing the cruciate ligaments
The knee from the side. The PCL sits deep in the middle of the joint and stops the shin bone sliding backward.

It is a technically harder operation than an ACL reconstruction. The attachment on the back of the shin bone sits deep in the knee, close to the major blood vessels behind it, which is why the operation takes care and why not every surgeon offers it.

Recovery: gravity is the problem

Here is the thing that makes PCL recovery different from everything else. When you lie on your back with your knee bent, gravity pulls your shin bone backward — exactly the direction the new graft is meant to resist. Your hamstrings pull it the same way.

So PCL rehabilitation is built around keeping the shin bone supported: the brace holds it forward, exercises are often done face-down rather than on your back, and hamstring work is kept out of the program early. When your therapist asks you to lie on your stomach, that is why.

  • Weeks 0–4Brace locked straight. You may put full weight on the leg — but only with the brace locked, and that includes sleeping in it. Therapy starts within a few days. Aspirin 81 mg twice daily for two weeks. Quadriceps work from the start; no hamstring work at all.
  • Weeks 5–8The brace opens gradually — to about 30 degrees, then about 60. Strengthening begins, still quad-focused.
  • Weeks 9–12Brace unlocked, full weight, motion progressing toward full. Advanced strengthening.
  • Through ~4 monthsA dynamic PCL brace stays on until around four months. Four months in a brace is a long time and it is the part patients find hardest — it is also the part that determines whether the graft stays tight.
  • 6 months onwardRunning, then multidirectional work, then sport.

The risks, honestly

  • The graft stretches out The characteristic problem with PCL reconstruction. Even done well, some knees end up with a little residual laxity. It is usually much better than before, but a perfectly tight knee is not guaranteed — and that is the honest state of this operation everywhere, not just here.
  • Stiffness More common after PCL surgery than ACL surgery, partly because of the protected early phase.
  • Injury to the vessels behind the knee Rare, but the reason this operation demands care.
  • Front-of-knee pain Common during recovery, since so much of the rehabilitation is quadriceps work.
  • Blood clots The reason for the aspirin and staying active.
  • Arthritis later Reduced but not eliminated, especially if cartilage was damaged at the time of injury.
This page is general education. It describes how I approach this and what most patients experience. If anything here does not match what you were told in clinic, ask — your own instructions always come first.