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Ligament Injuries in the Knee |
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 As the largest joint in the body, the knee is a complex structure of
muscle, bone and ligaments. Two sets of ligaments - the cruciate and
the collateral ligaments - work together to stabilize the knee joint
during movement.
The cruciate ligaments cross each other inside the knee joint, holding
the knee in place during movement. As the ligament names imply, the
anterior cruciate ligament (ACL) is located at the front of the knee
and the posterior cruciate ligament (PCL) is found at the back. The ACL
and PCL connect the femur, or thighbone, to the tibia, or shinbone.
The collateral ligaments are located on the sides of the knee. The
medial collateral ligament (MCL) connects the femur to the tibia on the
inner side of the knee and the lateral collateral ligament (LCL)
connects the femur to the fibula, another bone in the lower leg, on the
outer side of the knee.
Although injury can occur to any of the knee ligaments, the most common
is tearing the ACL. Injury to the ACL also causes the greatest
instability to the knee joint. This is because the ACL allows the knee
joint to bend and turn easily, and prevents the tibia from sliding
under the femur when you move.
Athletes participating in sports requiring sudden pivots, turns and
similar maneuvers - such as soccer, football, basketball and skiing -
are at a greater risk of an ACL tear. According to the American Academy
of Orthopaedic Surgeons (AAOS), ACL injury commonly occurs by:
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Changing direction rapidly
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Slowing down when running
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Landing from a jump
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Direct contact, such as tackling
The AAOS also points out that after an ACL injury, you may not
immediately feel pain. You will most likely hear a popping noise and
feel your knee give out from under you. The knee usually swells within
a few hours of injury and there is pain when weight is put on the knee.
Treatment immediately after any ligament injury should include applying
ice and elevating the knee to control swelling until you are able to
see an orthopedic physician. Walking or running on an injured ACL could
damage the cartilage in your knee. A complete tear to the ACL will
require surgical reconstruction whereas a partial tear may not need
surgery.
Tears to the other knee ligaments can happen but are not as common as
ACL tears. In the PCL, sprains are more common than tears and occur
when the ligament is stretched too far during activity.
Like an ACL tear, a PCL sprain or tear makes the knee joint unstable.
If the PCL is torn, the tibia can begin to slip backwards causing the
femur and tibia to rub against each other, which breaks down cartilage
over time and may lead to arthritis.
The MCL helps stabilize the knee joint by preventing the joint from
widening. As a result, injury to the MCL is usually caused by impact to
the outside of the knee. The blow causes the knee to collapse and the
joint widens because the MCL is overstretched.
Because all of the ligaments work together to stabilize the knee, MCL
tears can be isolated injuries or part of a more complex injury to the
knee. It is not uncommon to tear the ACL and MCL during the same injury.
Tearing or other injury to the LCL is not a common occurrence. To
determine the severity of any ligament tear or injury, an orthopedic
physician will test the knee joint to see if it stays in proper
position. Imaging studies, such as x-rays or MRI, are also used.
Regardless of a partial tear, complete tear, sprain or surgery to
reconstruct a torn ligament, a physical therapy program is put in place
to help strengthen the muscles and restore motion to the knee joint.
For more information about knee ligament injuries, or to schedule an
appointment, call Valley Orthopedic Associates at 425-656-5060.
Additional Resources:
American Academy of Orthopaedic Surgeons
Medline Plus (National Institutes of Health)
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