Sprained Knee

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Middle-aged woman suffering from knee pain at home, closeup.

A sprained knee injury occurs when a knee ligament suffers overstretching, tearing or rupturing due to sudden forces or blows to the knee. Although this type of injury may theoretically involve any of the ligaments of the knee, the most serious sprains usually involve the anterior cruciate ligament. Symptoms may include pain and swelling around the knee as well as (in the most severe cases) knee instability and discoloration/bruising of the skin around the knee. If the knee sprain is mild or moderate in severity, your doctor may suggest treating it at home by resting, icing, compressing and elevating your knee as much as possible. If the sprain is a serious one and your ligaments have been ruptured, knee surgery may be necessary to correct the injury.

Types Of Sprain

Sprained knee injuries can be classified both as to their severity as well as their type (i.e. which of the knee ligaments has been damaged).

Severity Of Sprain

Knee sprains can be classified as one of grades I, II or III depending on their severity:

  • A grade I sprained knee usually involves overstretching of one or more ligaments, with microscopic tearing of the ligament as a result;
  • If your sprain is grade II in severity, at least one ligament has suffered a partial (not complete) tear and you may experience moderate knee instability;
  • Individuals who have suffered a grade III sprained knee may have experienced complete rupturing of a ligament. Alternatively, the ligament may have become detached from the adjacent bone; This will usually result in moderate to severe knee instability as well as skin discoloration and bruising around the knee.

Type Of Sprain

The knee has 4 ligaments that play major roles in stabilizing the joint. First, there are the anterior and posterior cruciate ligaments (ACL & PCL). These are mainly there to stabilize the knee and protect it against front to back or back to front forces or blows. These two ligaments intersect at the center of the knee in the pattern of a cross (hence the use of the word “cruciate”).

Second, there are also the medial collateral and lateral collateral ligaments (MCL & LCL). Their role is to protect the joint from sideways blows, either left to right or vice versa. The MCL runs along the inside of the knee, while the LCL goes around the outer knee.

ACL or PCL Sprains

Sprains of the anterior cruciate ligament are usually the result of blows or forces applied to the front or back of the knee. Actions such as stopping suddenly from a full out sprint (and using your knee as a brake) or experiencing a blow to the front or back of the knee can cause this type of injury. This type of incident typically occurs during participation in sports such as football or soccer. Contact sports like hockey can also cause ACL sprains.

Many PCL sprains can also occur during motor vehicle collisions in which an occupant of a front seat hits his or her knee against the dashboard.

MCL or LCL Sprains

These types of knee sprains usually occur when your knee experiences a blow in a side to side (lateral) direction. The medial collateral ligament (MCL) sits on the inside of the joint and protects the knee from forces or blows on the outside of the joint. As a result, these types of blows can cause tearing or rupturing of the MCL.

You may also experience an MCL sprain if you fall in a way that causes your lower leg to twist outward relative to your upper leg.

The LCL sits on the outside of the knee joint and protects the knee from blows to the inner knee. However, because the opposing knee usually protects the joint from blows of that nature, LCL sprains are relatively unusual.

As with ACL and PCL knee sprains, MCL sprains typically occur while you are playing sports, especially those requiring frequent and sharp directional changes while running at high speed. Football, basketball and rugby are good examples of such sports.

Symptoms Of A Sprained Knee

If you suffer a sprained knee, the injury may announce itself as follows

  • A distinct “popping” or snapping” sound or sensation in the knee at the time you incur the injury. This particular symptom tends to be more common in cases of grade III sprains when a ligament is completely ruptured;
  • Pain and swelling in the region of the knee. These are usually more severe in cases of grade III sprains or those involving the ACL;
  • Knee instability, or a feeling that your knee “gives way” when you try to put your regular body weight on it. Again, this is more common in cases of sprains that are ACL injuries, grade III sprains or both;
  • Skin discoloration and bruising, especially in cases of more severe (grade III) knee sprains.

Treatment Of A Sprained Knee

If your injury is a mild or moderate sprain, the first option for your doctor may be to try a conservative approach.Surgery is usually an option for more severe sprains or those that resist conservative treatments.

Conservative Treatment

This will involve some or all of the following home based treatment options:

  • Resting your knee to allow the injured ligaments to heal naturally. To avoid stressing the ligaments and retarding their recovery, your doctor will advise refraining from athletic activity (especially if it involves running or jumping) for a while;
  • To further support the injured ligaments, you may also be advised to consider taking steps like wearing a hinged knee brace or knee stabilizer. These will provide lateral support to your knee and so help to protect the MCL and LCL ligaments. A hinged brace will also help to protect against knee hyperextension and, by so doing, will also protect the ACL and PCL ligaments;
  • You can take further steps to allow your knee ligaments to recover, including using a cane or crutches, to reduce the amount of body weight you put on your sprained knee;
  • Icing your knee will help to reduce its pain and inflammation. A cold compress will also help to achieve these objectives. If you require still more relief of pain and inflammation (e.g. for a grade III knee sprain), your doctor may be willing to prescribe a non steroidal anti inflammatory medication for this purpose;
  • Applying compression to your knee by wearing a knee sleeve will also help to improve blood circulation and speed its recovery;
  • Elevating your knee above heart level as much as possible (e.g. when lying or sitting down) will also help to improve blood circulation. This will promote recovery from your knee sprain.

Surgical Treatment

For grade III sprains, or those that prove resistant to home based treatments, doctors may consider surgical treatment.

Using arthroscopic technology (i.e. using instruments guided by a very small camera), a surgeon can operate to graft a piece of ligament from another part of your knee to repair the ruptured ligament. Alternatively, he or she may use a piece of ligament from a donor.


Once your conservative or surgical treatment is complete and healing is underway, you will likely need to commence a period of rehabilitative exercises under the supervision of a physiotherapist.

Although these exercises may seem to some to be unnecessary, they are actually extremely important to returning your knee to full health. Without it, you will be at risk of experiencing another knee sprain or of having chronic knee weakness or instability after you return to your normal activities. The key is to be patient, focus on the long term future and follow your rehabilitation program conscientiously. It will pay off in the long run.

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