Your knee is the largest joint in your body, and within that joint are bones, cartilage, ligaments, and tendons. When you bend, turn, jump, or walk, the ligaments in the knee keep the joint stable. The thick layer of cartilage between the femur and tibia (the bones that join at the knee) absorb the impact of and distribute the weight of your body when you move. Once in a while, however, such as during a soccer game or when missing your step off a curb, you may experience a sprained knee.


What caused the sprained knee?


A sudden impact or twist sometimes stretches or tears the ligaments. Too much sudden weight might put too much pressure on the muscles, ligaments, or tendons. This can also result in stretching or tearing. This injury is known as a knee sprain. If the injury affects the anterior cruciate ligament (one of the four ligaments in the knee,) the injury may be called a "torn ACL," an injury familiar to athletes and those who follow sports.


Understand the Anatomy of the Knee


There are two major leg bones that meet at the knee; these are the tibia and the femur. Supporting and protecting these two bones are four ligaments: the anterior cruciate ligament (ACL), the posterior cruciate ligament (PCL), the medial collateral ligament (MCL), and the lateral collateral ligament (LCL.) The two cruciate ligaments cross each other in an "X" shape, holding the bones in place and providing stabilization. The two collateral ligaments are positioned on either side of the knee and provide a powerful brace the keeps the tibia in an appropriate position.


Identify the Severity of the Injury


Before beginning treatment, you or your health care provider will need to determine the severity of the sprained knee. These injuries are separated into three categories, including Grade I, Grade II, and Grade III, or mild, moderate, and severe, respectively. A mild knee sprain stretches the ligament and causes only microscopic tears that don't significantly affect the knee's ability to support your weight. A moderate knee sprain causes some instability and an unreliable ability to support your weight. Finally, a severe sprain means the ligament has been completely torn and the knee is unstable.


Symptoms of Sprained Knee


When the ACL is injured, you may experience the following symptoms:

If the PCL has been injured, you'll probably experience:

An injury to the MCL often results in:

A sprain on the LCL generally causes:

Appropriate treatment of your sprain depends, in part, on which ligament is injured. With information about the type of movement that caused the injury, the severity of the injury, and the symptoms you're experiencing, the doctor may recommend a treatment course.


Sprained Knee Injury

Meniscal Tears


In addition to sprains, the layer of cartilage between the bones in the joint (the meniscus) can also be injured. This cartilage actually consists of two menisci: the lateral and the medial menisci. Both of these menisci are between the femur and tibia and are shaped like horseshoes. Tears may occur in the menisci during contact sports, because of degeneration over time, or because a combination of both circumstances.

As with ligament sprains, meniscus tears may happen in contact sports during jumps, uncontrolled twisting, and quick changes in direction. If other knee injuries happen, such as a torn ACL, the meniscus may also become injured. If you experience a meniscus tear, you'll probably have some of the same symptoms you would have experienced with a ligament sprain, including:

  • Knee pain
  • Swelling in the joint
  • A popping sensation
  • Trouble bending or straightening the joint
  • A tendency for the knee to lock up

When you've suffered a meniscal tear, you probably won't feel much pain until the inflammation begins. At this point, your knee will probably become very painful.


Making the Diagnosis

You don't need to call a professional every time you experience knee injuries, but some injuries require medical attention. If your knee becomes painful or swollen, it cannot bear weight, and it feels as if it will buckle, you should get quick medical attention.

When you meet with your trainer or doctor, the health care provider may ask which type of movement caused the injury, whether you heard a pop, how long before you noticed swelling, how severe the pain is and whether it began immediately following the injury, and whether you can put weight on the joint. Depending on the severity of the injury, the professional may follow up the examination with diagnostic tests, such as X-rays or an MRI. These tests may be necessary to distinguish between a torn ligament and a tear in the meniscus.

Fortunately, nearly everyone who is diagnosed with knee sprains can recover fully from their injuries when they receive proper treatment and participate in a good recovery program. This positive prognosis is true for ACL, PCL, MCL, and LCL injuries. However, there are some people who may experience osteoarthritis pain many (15 to 25) years after recovering from ACL or PCL sprains.

Treatment for Grade I or Grade II Sprains

Treatment for Grade III Sprains

Treatment for Meniscal Tears


Once you've experienced a knee injury, and long after the pain has receded, you'll be motivated to prevent the situation from happening again. Some of the best ways to avoid knee injuries are to warm up before participating in sports and athletic activities, exercising the leg muscles around the knee, wearing appropriate shoes that support your feet, discussing your activities with your health care provider, and investing in top-quality equipment for your activity.

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