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Knee Sprain: Classifications, Causes, Symptoms, Risk Factors

What is a Knee Sprain?

A knee sprain is one of the common injuries occurring to the knee joint. It occurs due to the overstretching of one of the knee ligaments causing the fibers to tear resulting in a knee sprain. Knee sprain is a condition where there is an injury or damage to any one of the ligaments in the knee. The 4 commonly injured ligaments in knee sprain are:

  1. Medial Collateral Ligament (MCL): Located in the inner knee joint.[1]
  2. Lateral Collateral Ligament (LCL): Located in the outer knee joint.[2]
  3. Anterior Cruciate Ligament (ACL): Located deep inside the knee.[3]
  4. Posterior Cruciate Ligament (PCL): Located deep inside the knee.

Knee Sprain

Can You Sprain Your MCL?

MCL or Medial Collateral Ligament is situated inside the knee joint. The 4 ligaments grip the bones together. The function of MCL or medial collateral ligament is to connect tibia- the top of shin bone with femur- the bottom of thigh bone. Also, all the 4 ligaments function to provide strength and firmness to the knee joint. When this MCL ligament is affected by any injury then it is known as MCL Sprain.

Generally, How Long Should You Ice Your Sprained Knee?

Swelling and pain caused due to knee sprain can be reduced by keeping it cool. Use ice or a cold pack to reduce the swelling. The ice should be applied at least 20 minutes on the injury for a minimum of three times a day. The swelling will start reducing after 2 to 3 days, then heat can be applied to minimize pain in the area.

Classification or Grades of Knee Sprain

  1. Grade 1 Knee Sprain: There is a minor tear where less than 10% of the fibers are torn or damaged. Grade 1 knee sprain usually heals on its own.
  2. Grade 2 Knee Sprain: In this grade, the knee sprain injury is more severe and more fibers are torn, but the ligament is not damaged. This grade can be further divided into grade 2- and 2+ sprain.
  3. Grade 3 Knee Sprain: There is complete rupture of the ligament in Grade 3 Knee Sprain and it usually requires surgery for repair.

Causes of Knee Sprain

Majority of the knee sprains result from a forceful movement or extreme impact on the knee joint such as twisting, which causes over-stretching of the ligament. ACL injury can be caused due to tackles in sports like football and rugby, twisting of the upper body when the foot is firmly planted on the ground etc. Injury to the MCL is usually caused as a result of prolonged stress on the ligament leading to stretching and inflammation of the ligament without causing any actual tear. Over pronation of the foot along with weak hip abductors causes the knee to fall inwards and damage the MCL.

Signs and Symptoms of a Knee Sprain

Signs or symptoms of a knee sprain may differ according to the type of the ligament affected. These are explained below as follows:[4]

Signs and Symptoms of Anterior Cruciate Ligament (ACL) Knee Sprain

The following are the signs and symptoms of anterior cruciate ligament (ACL) knee sprain:

  • If there is a snapping sound during the injury then, consider it as a sign of anterior cruciate ligament (ACL) sprain.
  • One will observe the symptom of knee joint swelling within few hours of the injury.
  • You will not be able to participate in any activity due to the symptoms of severe pain associated with this type of knee sprain
  • Symptoms of black and blue discoloration is observed around the knee in the case of anterior cruciate ligament (ACL) knee sprain
  • One can observe the symptom of instability of the knee, knee joint gets buckled/give up when you try to stand.

Signs and Symptoms of Posterior Cruciate Ligament (PCL) Knee Sprain

The following are the signs and symptoms of posterior cruciate ligament (PCL) knee sprain:

  • Symptom of mild swelling in the knee is seen in posterior cruciate ligament (PCL) sprain, sometimes along with joint instability.
  • Slight difficulty in movement of the knee can also be a symptom of posterior cruciate ligament (PCL) knee sprain.
  • Slight pain behind the knee that aggravates when you bend the knee joint is also a common symptom of posterior cruciate ligament (PCL) knee sprain.

Signs and Symptoms of Medial Collateral Ligament (MCL) Knee Sprain

Below mentioned are the signs and symptoms of medial collateral ligament (MCL) knee sprain:

  • Symptoms of swelling and pain in the knee is seen in the medial collateral ligament (MCL) sprain.
  • Outwards buckling of the knee joint is also a sign and symptom of medial collateral ligament (MCL) knee sprain.
  • The area where the ligament is torn gets tender.

Signs and Symptoms of Lateral Collateral Ligament (LCL) Knee Sprain

Following are the signs and symptoms of lateral collateral ligament (LCL) knee sprain:

  • Inside buckling of the knee is the usual sign and symptom of the lateral collateral ligament (LCL) sprain.
  • Swelling and pain in the knee.
  • The area outside the torn ligament gets tender.

Risk Factors That Contribute to a Knee Sprain

The risk factors involved in causing knee sprain are explained ahead as follows:

  • Lack of conditioning can lead to knee sprain: Poor conditioning of the knee and thigh muscles may make them weak and lead to injury and cause knee sprain.
  • Fatigue: If the muscles are tired then they will not be able to provide support to the knee joint thereby, making you more prone to a knee sprain during stress or force of any kind.
  • Lack of warming-up: Improper warm-up before vigorous exercises or sports can result in loosening of the thigh muscles. This increases the range of motion of the joint making it less tight and more prone to knee sprain and tears.
  • Natural surrounding conditions: Moving across slippery or irregular surfaces can cause injury or sprain to the knee.
  • Improper Footwear: Footwear that is ill-fitted and poorly maintained can lead to increased risk of knee sprain.[5]

Complications Involved in a Knee Sprain

The major problem that may arise during the knee sprain is immobility or difficulty to walk. Long-term injuries may be caused due to disease of the joint that may result in permanent damage and loss of function.

Tests to Diagnose a Knee Sprain

How to Detect a Knee Sprain?

The factors leading to the knee sprain can tell what happened to the knee joint:

  • Cause of the knee sprain like any sudden movement, stop, twist, hyperextension, or pivot.
  • If there was a popping sound inside the knee joint.
  • Time taken by the swelling to show up.
  • Severe knee pain immediately accompanied by the sprain or not.
  • Unsteadiness of the knee and unable to bear body weight.

When you go to a doctor he will ask the above given questions and examine both of your knees, comparing the sprained one with the normal. The doctor will first check for any signs of deformity, swelling, tenderness, discoloration, or presence of fluid. If the pain and swelling is not too severe, then the doctor will check the intensity of damage by evaluating the range of motion of the knee joint and its strength. You will have to bend your knee joint, pull forward, or gently push backward.

If the examination confirms any probability of sprain, then you will require going through diagnostic tests for further evaluation. You may require to give X-rays, MRI, or Arthroscopy to check the extent of the knee sprain.


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Team PainAssist
Team PainAssist
Written, Edited or Reviewed By: Team PainAssist, Pain Assist Inc. This article does not provide medical advice. See disclaimer
Last Modified On:October 5, 2020

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