Knee ligaments are bands of connective tissue that connect and stabilize the femur (thigh bone) to the tibia (shin bone). The five primary ligaments in the knee include the anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), medial collateral ligament (MCL), lateral (or fibular) collateral ligament (LCL) and the posterolateral corner (PLC).
Knee ligaments are torn or stretched when the forces applied to the ligament exceed their strength. These forces can come from obvious causes, like football tackles, motor vehicle accidents or falls. They can also occur from non-contact injuries, where an athlete attempts to quickly change direction while running. Many noncontact ACL injuries occur in basketball, football and soccer. Many PCL injuries occur in motor vehicle accidents.
Symptoms of knee ligament injuries usually are “popping,” instability, pain and swelling. The swelling in the knee may not be immediate. Instability is the sensation that the knee bones are “sliding” or “shifting” out of place.
Physical examination and history are the most important elements in obtaining a diagnosis. As the knee is stressed in various positions, the integrity of the different ligaments is checked. Imaging studies such as X-rays can be helpful to identify bony injuries. Magnetic resonance imaging (MRI) can be very helpful in identifying ligament injuries.
Each knee ligament injury is unique. Some injuries may be managed with nonoperative care and rehabilitation. Some injuries require surgical treatment with ligament repair or reconstruction. Most knee ligament injuries that are treated surgically can be successfully treated arthroscopically. Treatment decisions are made based on the physical examination of the knee, the imaging studies, and the activity level and expectations of the patient. Whether the decision is operative or nonoperative, a level of rehabilitation needs to be performed.
It is extremely difficult to make general conclusions regarding outcomes, as each injury is unique. These injuries may range from minor injuries from which recovery is complete, to devastating injuries that make walking difficult even after appropriate treatment. Compared to chronic injuries, early treatment of knee ligament injuries has often shown improved outcomes.
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