KNEE · PCL INJURY
PCL injury: the ligament that is usually missed, and often does not need surgery.
The PCL is torn far more often than it is diagnosed, because the knee usually still walks and the classic sign is only visible if someone looks for it. Most isolated PCL injuries do well without surgery. The ones that need reconstruction are a specific group, and this explains which.
Dr. Prashant Parate · Shoulder, Knee & Sports Injury Surgeon · In orthopaedic practice since 2010, DNB-qualified since 2012 · Jupiter Hospital (Baner) & Sainath Hospital (Moshi, PCMC) · Reviewed July 2026
Related: Multi-Ligament Knee Injury
What the PCL does
The posterior cruciate ligament sits behind the ACL in the centre of the knee and is the thicker and stronger of the two. Its job is to stop the shin bone sliding backwards on the thigh bone, and it is the main restraint when you go down stairs or a slope, and when you push off.
Unlike the ACL, a torn PCL often has some capacity to heal in a lengthened position, and the knee can remain functional. This is exactly why the injury goes undetected: the patient walks, the X-ray is normal, and the diagnosis is never made.
How it tears
The dashboard injury. The knee is bent and the front of the shin strikes something solid, driving the tibia backwards. In a car this is the dashboard. On a two-wheeler it is the ground or another vehicle, and this is the commonest mechanism we see.
A fall onto a bent knee with the foot pointing downward, which drives the shin back in the same way.
Hyperextension or a severe twist, which typically damages other ligaments at the same time.
In a young patient the ligament may pull off with a fragment of bone rather than tearing in its middle, which is a bony avulsion and is treated completely differently. See the avulsion fixation guide.
The sign that makes the diagnosis
With both knees bent to a right angle and the feet flat, look at the two knees from the side. In a PCL-deficient knee the front of the shin bone sags backwards compared with the normal side, and the usual step at the front of the joint disappears.
This matters because of a trap. If the examiner does not notice the sag and then pulls the shin forward, it travels further than normal and feels exactly like an ACL tear. A number of patients are told they have torn the ACL when in fact they have torn the PCL, and are then reconstructed for the wrong ligament. Comparing the two knees side by side prevents that.
Grades, and what they mean for you
| Grade | What it means | Usual treatment |
| Grade I and II | Partial tearing. The shin sags a little but the step at the front is still present | Non-operative. Bracing and a specific quadriceps programme |
| Grade III | Complete tear. The step is gone or reversed. Other structures are often torn too | Assess the whole knee. Reconstruction considered, particularly if combined |
| Bony avulsion | The ligament is intact but has pulled off with its bone attachment | Fix the fragment back, ideally early. Excellent results |
The decision pathway
1. Is the PCL torn on its own, or with other ligaments?
This is the most important question on the page. An isolated PCL injury often does very well without surgery. A PCL torn together with the outer side or the inner side of the knee behaves completely differently and usually needs reconstruction. Deciding this correctly requires examining every structure, not just the PCL. Isolated and combined are different diseases.
2. Is it a bony avulsion?
If the ligament has pulled off with a piece of bone, fixing that fragment back gives bone-to-bone healing, which is more reliable than reconstructing a ligament. This should be done within the first few weeks, before the fragment cannot be reduced. Fix it, and fix it early.
3. Is it isolated, partial, and have you completed proper rehabilitation?
Then non-operative treatment is the right answer for most patients, and the results are good. The programme is specific: bracing that supports the shin from behind, and a quadriceps-focused programme, because a strong quadriceps actively compensates for the missing PCL. Hamstring work is deliberately limited early, since the hamstrings pull the shin backwards, which is exactly what the PCL was preventing. Rehabilitation, done properly.
4. Has proper rehabilitation failed, with continuing instability or pain?
Persistent difficulty going down stairs or slopes, a sense of the knee giving way backwards, or pain developing at the front of the knee and on the inner side, all suggest the knee is not coping. That is when reconstruction becomes reasonable in an isolated injury. Reconstruction after a fair trial.
5. Is the knee bow-legged, and has this been going on for years?
A long-standing PCL-deficient knee that is also bow-legged will stretch out any reconstruction, because the limb keeps driving load in the direction the reconstruction is trying to resist. In that situation the alignment is corrected first, and sometimes that alone is enough to make the knee comfortable. Correct the alignment before, or instead of, reconstructing.
What happens if it is left
Many people function well for years with a PCL-deficient knee, particularly if the injury was partial and the quadriceps is strong. But there is a recognised long-term pattern. The constant backward sag increases pressure on the cartilage behind the kneecap and in the inner compartment, and arthritis in those two areas is more common in these knees over the following decades.
That risk is a reason for taking the rehabilitation seriously and for monitoring the knee, rather than an argument for operating on every PCL tear. Reconstruction has not been shown to reliably prevent that arthritis, which is an honest limitation worth knowing.
Reconstruction and recovery
PCL reconstruction is done arthroscopically. A graft is passed through tunnels to recreate the ligament, using either a tunnel through the shin bone or a technique that attaches the graft directly onto the back of the tibia, each with its own advantages. Where other ligaments are torn, they are addressed in the same operation.
Recovery is slower and more demanding than after ACL reconstruction, and patients should know this in advance. The graft is working against gravity, which constantly pulls the shin backwards, so early protection is more restrictive. A brace supporting the shin from behind is used for around three months, weight-bearing is protected initially, and hamstring exercises are deliberately delayed. Return to demanding sport is generally around nine to twelve months.
Frequently asked questions
I was told I have a PCL tear but no surgery is needed. Is that right?
For an isolated partial PCL injury, very likely yes, and that advice reflects good evidence rather than neglect. What matters is that the rest of the knee was properly examined to confirm the injury really is isolated, and that you are given a specific rehabilitation programme rather than told simply to rest.
Why is my rehabilitation different from my friend’s ACL programme?
Because the two ligaments resist opposite movements. After PCL injury the hamstrings are the problem, since they pull the shin backwards in the direction the PCL was resisting, so hamstring work is limited early and quadriceps work is emphasised. Following an ACL programme after a PCL injury actively works against you.
My knee was told to be an ACL tear. Could it actually be the PCL?
It can happen. If the backward sag is not noticed, pulling the shin forward from that sagged position gives excessive movement that mimics an ACL tear. If your injury was a dashboard-type impact or a fall onto a bent knee, and the diagnosis was made without comparing both knees side by side, it is worth having it reassessed.
Can I run and play sport with a PCL-deficient knee?
Many people do, particularly with an isolated partial injury and a strong quadriceps. Straight-line running is usually fine. Difficulty tends to come with going downhill, downstairs, and deceleration. If those are limiting you despite good rehabilitation, that is the argument for reconstruction rather than a scan finding.
How long should I wear the brace?
For a non-operative injury, typically several weeks in a brace designed to support the shin from behind, rather than an ordinary knee sleeve which does nothing mechanically. After reconstruction it is longer, usually around three months, because the graft needs protecting from the constant backward pull of gravity.
Key takeaways
- Isolated PCL injuries mostly do well without surgery. Combined injuries mostly do not.
- The diagnosis is made by comparing both knees from the side, looking for the backward sag.
- A PCL tear can be mistaken for an ACL tear if the sag is not noticed first.
- Bony avulsions should be fixed early and do very well.
- Rehabilitation is quadriceps-led and limits hamstring work, which is the opposite of an ACL programme.
- A bow-legged, chronically PCL-deficient knee needs the alignment addressed or the reconstruction will stretch.
Knee not right since a dashboard or two-wheeler injury?
Bring your films. A proper examination comparing both knees will establish whether the PCL is involved, whether it is isolated, and whether you need rehabilitation or reconstruction.
Appointments by phone
Sainath Hospital, Moshi, PCMC
86000 05886
Mon to Fri, 10 am to 4 pm · Sat, 10 am to 12 noon
Jupiter Hospital, Baner, Pune
020 2799 2150
Mon to Sat, 5.30 pm to 6.30 pm · OPD 5
This page is patient education, not a substitute for consultation. Treatment decisions require clinical examination and imaging review. Last medically reviewed: July 2026 by Dr. Prashant Parate, DNB Orthopaedics, Fellowship in Arthroscopy & Sports Medicine (Thammasat University Hospital, Thailand). MMC Reg. 2006042129.