More than 6 million people visit orthopaedic surgeons
each year because of knee problems. The knee is the largest joint in the
body and is vital to movement. Two sets of ligaments in the knee give it
stability: the cruciate and the collateral ligaments.
The cruciate ligaments are located inside the knee joint and connect
the thighbone (femur) to the shinbone (tibia). They are made of many
strands and function like short ropes that hold the knee joint tightly
in place when the leg is bent or straight. This stability is needed for
proper knee joint movement.
The name, cruciate, derives from the word crux, meaning cross, and
crucial. The cruciate ligaments not only lie inside the knee joint, they
crisscross each other to form an "x". The cruciate ligament
located toward the front of the knee is the anterior cruciate ligament (ACL),
and the one located toward the rear of the knee is called the posterior
cruciate ligament (PCL).
The ACL prevents the shinbone from sliding forwards beneath the
thighbone. The ACL can be injured in several ways:
Recognizing an ACL injury
If you injure your ACL, you may not feel any pain immediately.
However, you might hear a popping noise and feel your knee give out from
under you. Within 2 to 12 hours, the knee will swell, and you will feel
pain when you try to stand. Apply ice to control swelling and elevate
your knee until you can see an orthopaedic surgeon.
If you walk or run on an injured ACL, you can damage the cushioning
cartilage in the knee. For example, you may plant the foot and turn the
body to pivot, only to have the shinbone stay in place as the thighbone
above it moves with the body.
Diagnosing an ACL injury
A diagnosis of ACL injury is based on a thorough physical examination
of the knee. The exam may include several tests to see if the knee stays
in the proper position when pressure is applied from different
directions. Your orthopaedist may order an X-ray and MRI (magnetic
resonance imaging) or, in some cases, arthroscopic inspection.
A partial tear of the ACL may or may not require surgical treatment.
A complete tear is more serious. Complete tears, especially in younger
athletes, may require reconstruction.
Treating ACL tears
Both nonoperative and operative treatment choices are available.
The posterior cruciate ligament, or PCL, is not injured as frequently
as the ACL. PCL sprains usually occur because the ligament was pulled or
stretched too far, a blow to the front of the knee, or a simple misstep.
PCL injuries disrupt knee joint stability because the shinbone can
sag backwards. The ends of the thighbone and shinbone rub directly
against each other, causing wear and tear to the thin, smooth articular
cartilage. This abrasion may lead to arthritis in the knee.
Treating PCL injuries
Patients with PCL tears often do not have symptoms of instability in
their knees, so surgery is not always needed. Many athletes return to
activity without significant impairment after completing a prescribed
However, if the PCL injury pulls a piece of bone out of the top of
the shinbone, surgery is needed to reattach the ligament. Knee function
after this surgery is often quite good.
The collateral ligaments are located at the inner side and outer side
of the knee joint. The medial collateral ligament (MCL) connects the
thighbone to the shinbone and provides stability to the inner side of
the knee. The lateral collateral ligament (LCL) connects the thighbone
to the other bone in the lower portion of your leg (fibula) and
stabilizes the outer side.
Injuries to the MCL are usually caused by contact on the outside of
the knee and are accompanied by sharp pain on the inside of the knee.
The LCL is rarely injured.
Collateral ligament injuries
If the medial collateral ligament (MCL) has a small partial tear,
conservative treatment usually works. Remember the acronym RICE: Rest,
Ice, Compression, Elevation.
Rest the knee to give the ligament time to heal. Ice can be applied
two or three times a day for 15 to 20 minutes each time.
Compress the injury to limit swelling. You may have to wear a bandage
or brace for a while.
Elevate the knee whenever possible.
You should also consult your physician about a course of
rehabilitation exercises for good healing.
If the collateral ligament is completely torn or torn in such a way
that ligament fibers cannot heal, you may need surgery. Repair may bring
good results, with a return to good knee stability. After satisfactory
rehabilitation, many people resume their previous levels of activity.
A rehabilitation plan is needed if you have a cruciate or collateral
ligament injury. Most rehabilitation plans include: