A PCL injury is a knee joint sprain or tear of the posterior cruciate ligament, the ligament that stops your shinbone sliding BACKWARD under your thighbone. It’s usually hurt by a hard blow to the front of a bent knee, for example:
- the knee hitting the dashboard in a car crash,
- or a fall onto a bent knee in sport
The good news is that most PCL injuries where it’s the only thing hurt are treated WITHOUT surgery. The treatment is protection early on, then a lot of thigh muscle work. Your quadriceps pull the shinbone forward, which does part of the PCL’s job for it.
Typical return to sport:
- Grade 1 and 2 (milder injuries): many athletes are back training in about 2 to 3 months
- Grade 3 (complete tear) without surgery: often about 4 to 6 months
- After PCL reconstruction: about 9 to 12 months
What the PCL does and how it gets hurt
The PCL runs through the middle of the knee, just behind the ACL. It is thicker and roughly twice as strong as the ACL, so it takes a big force to injure it. PCL injuries are much less common than ACL injuries.
- Dashboard injury: the bent knee hits the dashboard and the shinbone is driven backward
- A fall onto a bent knee: especially with the toes pointed, so the top of the shinbone takes the impact
- Twisting or overstraightening: the knee bends backward or twists hard in sport
- Major trauma: a knee dislocation, where several ligaments tear at once
Symptoms
- Pain and swelling: usually coming on fairly quickly after the injury
- Stiffness and limping: the knee doesn’t want to bend or take full weight
- Feeling unsteady: often most noticeable going down stairs or slopes
- Surprisingly mild symptoms: some people walk off an isolated PCL injury with only mild discomfort, so it can be missed at first
The three grades
A doctor or physio bends your knee to a right angle and gently pushes the shinbone backward to see how far it moves. An MRI scan checks the PCL and looks for other damage.
- Grade 1: a partial tear. The shinbone moves back only a little, up to about 5 millimeters
- Grade 2: a bigger tear. The shinbone moves back more, about 6 to 10 millimeters
- Grade 3: a complete tear. The shinbone sags back more than 10 millimeters, and other ligaments are often injured too, especially at the outer back corner of the knee
With a torn PCL, your thigh muscle becomes the ligament’s backup.
Treatment without surgery
- Early protection: a brace, sometimes one that supports the back of the shinbone to stop it sagging backward. Crutches if you’re limping badly
- Quadriceps first: thigh tightening and straight leg raises in the first days, building to leg press, squats and step-ups
- Go easy on the hamstrings early: the hamstrings pull the shinbone backward, the direction the PCL resists. Heavy hamstring curls are usually held back in the early weeks
- Keep it moving: work steadily on bending and straightening. A stationary bike helps
- Balance and sport skills: one-leg balance, then running, jumping and changing direction once strength is close to the other leg
Many people return to full sport this way and do well.
Over many years, a PCL-injured knee has a higher chance of developing arthritis, so keeping the leg strong and getting persistent problems reviewed matters. See knee arthritis.
When is PCL surgery needed?
- Combined injuries: a knee dislocation or tears of several ligaments. The MCL, the ACL or the outer corner of the knee may need repair at the same time. See ACL reconstruction recovery
- A bone avulsion: the ligament pulls a piece of bone off the shinbone. The fragment can often be fixed back in place
- Ongoing instability or pain: the knee still gives way or hurts after a proper period of rehab
Reconstruction replaces the ligament with a graft of tendon. Full recovery takes 6 to 12 months. The AAOS OrthoInfo guide to PCL injuries explains both paths.
Go to the emergency department if
- The knee looks deformed or out of place after an injury
- Your foot goes cold, pale, blue or numb. A knee dislocation can damage the artery and nerves behind the knee
- You can’t put any weight on the leg
- Your calf becomes painful, swollen or warm, especially if you’ve been on crutches or in a brace
See your doctor or physio if
- The knee still feels loose or gives way after a few months of rehab
- Swelling keeps coming back after activity
- The knee wobbles when you twist, or bends backward further than the other one
Most PCL tears don’t need a surgeon. They do need strong quads.