PCL injury

The posterior cruciate ligament (PCL) sits at the back of the knee joint and keeps the shinbone from sliding backward beneath the thighbone. Because it is the sturdier of the two cruciate ligaments, it tears far less often than the ACL, and usually only under a large force: the upper shin being driven backward in a car collision, for example, or a hard landing on a flexed knee.

• Pain and swelling that build over the hours after the injury
• Stiffness and a limp
• Difficulty walking, especially down stairs or slopes
• A feeling that the knee is unstable or might give out

Some isolated PCL tears cause fairly mild symptoms at first and can be overlooked.

• A collision in which the upper shin is jammed against a car's dashboard while the knee is flexed
• Falling onto a bent knee, often with the foot pointed down, in sports such as football and soccer
• The knee being forced backward (hyperextension) or twisted under a heavy load

High-energy injuries can tear the PCL along with other ligaments, and some dislocate the knee and injure nearby nerves and blood vessels.

A clinician compares the injured knee with the healthy one. With a PCL tear, the shinbone may sag backward when the knee is bent, or slide back farther than normal when gently pushed.

X-rays can show a piece of bone pulled off with the ligament, and stress X-rays can measure how far the shinbone moves backward. An MRI shows the ligament and other injuries inside the knee. After a high-energy injury, circulation and nerve function in the leg are checked carefully.

Many isolated PCL tears, especially partial tears, are treated without surgery. Care includes rest, ice, gentle compression, and elevation; a brace that supports the back of the shinbone to keep it from sagging; crutches for a time; and physical therapy that restores motion and builds strength, with special emphasis on the quadriceps muscles at the front of the thigh.

Surgery is more likely when the PCL is torn together with other ligaments, which usually requires reconstruction, or when a bone fragment has pulled away with the ligament. It may also be considered when an isolated tear leaves the knee unstable or painful despite rehabilitation. Because stitched PCL ends rarely heal, the ligament is usually rebuilt with a graft from the patient or a donor, typically using arthroscopic techniques.

Rehabilitation is gradual and focuses on motion, quadriceps strength, and protecting the healing ligament. After reconstruction, therapy starts within the first weeks, and full recovery generally takes many months. Combined ligament injuries tend to recover more slowly than isolated tears. Steady commitment to the rehabilitation program is one of the most important factors in getting back to activity, and follow-up visits help track the knee over time.

Many PCL injuries come from crashes or hard falls that cannot be fully prevented. Wearing a seat belt, keeping the leg muscles strong, and learning safe falling and tackling technique in sports can help.