Definition

A knee sprain is stretching or tearing of the ligaments that support the knee. Ligaments are strong bands of tissue that connect bones to each other.

Ligaments of the Knee

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© 2009 Nucleus Medical Art, Inc.

Causes

Knee sprains may be caused by:

  • Forced twisting of the knee
  • Stopping suddenly while running
  • Shifting your weight while running or skiing
  • Landing awkwardly after jumping
  • Blow to the outer or inner side of the knee
  • Blow to the front of the knee while the knee is bent and the foot is firmly planted on the ground

Risk Factors

These factors increase your chance of developing a knee sprain. Tell your doctor if you have any of these risk factors:

  • Playing sports
  • Poor coordination
  • Poor balance
  • Inadequate flexibility and strength in muscles and ligaments
  • Loose joints

Symptoms

Symptoms include:

  • Pain in the knee
  • Swelling, redness, warmth, or bruising around the knee
  • Decreased range of motion in the knee
  • Inability to stand on the affected leg
  • Tenderness where the injured ligament attaches to a bone in the knee
  • Swelling within the knee

Diagnosis

Your doctor will ask about your symptoms and how the injury occurred. The knee will be checked to see how stable the joint is and how severe the pain is. Tests may include:

  • X-rays —a test that uses radiation to take pictures of structures inside the body, especially bone (to assess if any bones are broken)
  • MRI scan —a test that uses a magnetic field to make pictures of structures to assess if a ligament has torn completely (less commonly used)

Grades

Knee sprains are graded according to their severity. The more ligaments that are involved means the more severe the injury.

  • Grade 1
    • Stretching and microtearing of ligament tissue
  • Grade 2
    • Partial tearing of ligament tissue
    • Mild instability of the joint when tested
  • Grade 3
    • Severe or complete tearing of ligament tissue
    • Significant instability of the joint

Grade 2 Sprain of Knee

Sprained ligament knee
© 2009 Nucleus Medical Art, Inc.

Treatment

Treatment includes:

  • Rest—Avoid putting any pressure on your knee by not walking on that leg.
  • Ice—Apply ice or a cold pack to the knee for 15-20 minutes, four times a day for two days. This helps reduce pain and swelling. Wrap the ice or cold pack in a towel. Do not apply ice directly to your skin.
  • Compression—Wrap your knee in an elastic bandage (eg, Ace bandage). This will limit swelling and provide some support for your knee. Be careful not to wrap the bandage too tight.
  • Elevation—Keep the injured knee raised above the level of your heart. Do this as much as possible for 24 hours or so. This will help drain fluid and reduce swelling. For severe sprains, you may need to do this for a couple of days.
  • Medication—Ask your doctor which pain medication you should use. Common ones include:
  • Brace—You may need to wear a brace. Your doctor may also recommend that you wear a brace when you return to sports. Although, the American Academy of Pediatrics recommends that children do not use braces.
  • Leg cast—If you have a severe sprain, you may need to wear a short leg cast for 2-3 weeks.
  • Rehabilitation exercises—Ask your doctor about exercises to restore flexibility, range of motion, and strength.
  • Surgery—This may be needed if a ligament is torn completely.

Prevention

To reduce your risk of spraining a knee:

  • Warm up and stretch before exercise. Cool down and stretch after exercise.
  • Take a break from sports and exercise when you feel tired.
  • Do exercises that strengthen the leg muscles.
  • Learn the proper technique for sports and exercise. This will decrease stress on all your muscles, ligaments, and tendons, including those around your knee. Also, wear the proper equipment.
  • Ask your doctor if you should use a brace.