Avulsion Fracture PCL Injury
The
posterior cruciate ligament is located in the back of the knee. It is one of
several ligaments that connect the femur (thighbone) to the tibia (shinbone).
The posterior cruciate ligament keeps the tibia from moving backwards too far.
An
injury to the posterior cruciate ligament requires a powerful force. A common
cause of injury is a bent knee hitting a dashboard in a car accident or a
football player falling on a knee that is bent.
Two
bones meet to form your knee joint: your thighbone (femur) and shinbone
(tibia). Your kneecap sits in front of the joint to provide some protection.
Bones
are connected to other bones by ligaments. There are four primary ligaments in
your knee. They act like strong ropes to hold the bones together and keep your
knee stable.
Collateral ligaments. These are found on the sides of your knee. The medial
collateral ligament is on the inside and the lateral collateral ligament is on
the outside. They control the sideways motion of your knee and brace it against
unusual movement.
Cruciate ligaments. These are found inside your knee joint. They cross
each other to form an "X" with the anterior cruciate ligament in
front and the posterior cruciate ligament in back. The cruciate ligaments
control the back and forth motion of your knee.
The
posterior cruciate ligament keeps the shinbone from moving backwards too far.
It is stronger than the anterior cruciate ligament and is injured less often.
The posterior cruciate ligament has two parts that blend into one structure
that is about the size of a person's little finger.
Injuries
to the posterior cruciate ligament are not as common as other knee ligament
injuries. In fact, they are often subtle and more difficult to evaluate than
other ligament injuries in the knee.
Many
times a posterior cruciate ligament injury occurs along with injuries to other
structures in the knee such as cartilage, other ligaments, and bone.
A
complete tear of the posterior cruciate ligament, back view.
Injured
ligaments are considered "sprains" and are graded on a severity
scale.
Grade 1 Sprains. The ligament is mildly damaged in a Grade 1 Sprain. It
has been slightly stretched, but is still able to help keep the knee joint
stable.
Grade 2 Sprains. A Grade 2 Sprain stretches the ligament to the point
where it becomes loose. This is often referred to as a partial tear of the
ligament.
Grade 3 Sprains. This type of sprain is most commonly referred to as a
complete tear of the ligament. The ligament has been split into two pieces, and
the knee joint is unstable.
Posterior
cruciate ligament tears tend to be partial tears with the potential to heal on
their own. People who have injured just their posterior cruciate ligaments are
usually able to return to sports without knee stability problems.
Cause
An
injury to the posterior cruciate ligament can happen many ways. It typically
requires a powerful force.
- A
direct blow to the front of the knee (such as a bent knee hitting a dashboard
in a car crash, or a fall onto a bent knee in sports)
- Pulling
or stretching the ligament (such as in a twisting or hyperextension
injury)
- Simple
misstep
The
typical symptoms of a posterior cruciate ligament injury are:
- Pain
with swelling that occurs steadily and quickly after the injury
- Swelling
that makes the knee stiff and may cause a limp
- Difficulty
walking
- The
knee feels unstable, like it may "give out"
During
the physical examination, your doctor will check all the structures of your
injured knee, and compare them to your non-injured knee. Your injured knee may
appear to sag backwards when bent. It might slide backwards too far,
particularly when it is bent beyond a 90° angle. Other tests which may help
your doctor confirm your diagnosis include X-rays and magnetic resonance
imaging (MRI). It is possible, however, for these pictures to appear normal,
especially if the injury occurred more than 3 months before the tests.
- X-rays. Although they will not show any injury to your posterior cruciate ligament, X-rays can show whether the ligament tore off a piece of bone when it was injured. This is called an avulsion fracture.
- MRI. This study creates better images of soft tissues like the posterior cruciate ligament.
Sagittal
and coronal T2-weitghted magnetic resonance images of the knee, showing upward
displacement of the PCL insertion at the tibia (a) and the displaced fragment
of the lateral tibial condyle (b and c).
- Nonsurgical Treatment
If
you have injured just your posterior cruciate ligament, your injury may heal
quite well without surgery Your doctor may recommend simple, nonsurgical
options.
RICE. When
you are first injured, the RICE method - rest, ice, gentle compression and
elevation — can help speed your recovery.
Immobilization. Your doctor may recommend a brace to prevent your knee
from moving. To further protect your knee, you may be given crutches to keep
you from putting weight on your leg.
Physical therapy. As the swelling goes down, a careful rehabilitation
program is started. Specific exercises will restore function to your knee and
strengthen the leg muscles that support it. Strengthening the muscles in the
front of your thigh (quadriceps) has been shown to be a key factor in a
successful recovery.
- Surgical Treatment
Your
doctor may recommend surgery if you have combined injuries. For example, if you
have dislocated your knee and torn multiple ligaments including the posterior
cruciate ligament, surgery is almost always necessary.
Rebuilding the ligament. Because sewing the ligament
ends back together does not usually heal, a torn posterior cruciate ligament
must be rebuilt. Your doctor will replace your torn ligament with a tissue
graft. This graft is taken from another part of your body, or from another
human donor (cadaver). It can take several months for the graft to heal into
your bone.
Procedure. Surgery to rebuild a posterior cruciate ligament is
done with an arthroscope using small incisions. Arthroscopic surgery is less
invasive. The benefits of less invasive techniques include less pain from
surgery, less time spent in the hospital, and quicker recovery times.
Surgical
procedures to repair posterior cruciate ligaments continue to improve. More
advanced techniques help patients resume a wider range of activities after
rehabilitation.
Whether
your treatment involves surgery or not, rehabilitation plays a vital role in
getting you back to your daily activities. A physical therapy program will help
you regain knee strength and motion. If you had surgery, physical therapy will
begin 1 to 4 weeks after your procedure.
How
long it takes you to recover from a posterior cruciate ligament injury will
depend on the severity of your injury. Combined injuries often have a slow
recovery, but most patients do well over time.
If
your injury requires surgery, it may be several weeks before you return to a
desk job - perhaps months if your job requires a lot of activity. Full recovery
typically requires 6 to 12 months.
Although
it is a slow process, your commitment to therapy is the most important factor
in returning to all the activities you enjoy.
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