What is a knee strain or sprain?

A knee strain occurs when a muscle or tendon is torn or stretched. The tendons are fibrous cords that connect muscles to bones.

A knee sprain occurs when the ligaments in the knee joint stretch or tear. Ligaments connect the bones of your lower leg to the bones in your thigh together in your knee joints.

Common related conditions
Anterior Cruciate Ligament (ACL) Injury Lateral Collateral Ligament (LCL) Injury Medial Collateral Ligament (MCL) Injury Posterior Cruciate Ligament (PCL) Injury

Causes of a knee strain or sprain

  • Injuries — trauma, sports injuries or falls that overstretch the joints and soft tissue that surround the knee and cause a knee sprain or strain.
  • Overuse — building up too quickly in a sport, such as running, can overwhelm the body and lead to knee strains or sprains.
  • Muscle weakness — muscles that can’t support the knee joints can cause a knee strain or sprain.
  • Reduced flexibility — tight muscles can restrict joint motion and lead to functional weaknesses at the knee joint to cause a knee strain or sprain.
  • Running form — overpronating when running or walking can increase stress to the knee and cause a knee strain or sprain.

Risk factors for a knee strain or sprain

  • Contact sports — participating in contact sports such as football, basketball and soccer put you at a higher risk for knee sprains or strains.
  • Prior knee strains or sprains — prior sprains or strains to the knee make you more likely to suffer another knee sprain or strain.
  • Improper footwear — wearing improper footwear can put additional pressure on the knee joint and cause a knee strain or sprain.

Symptoms of a knee strain or sprain

  • Pain and tenderness in the knee
  • Stiffness, bruising and swelling in the knee
  • Instability when walking
  • Popping noise when injured

Diagnosis of a knee strain or sprain

Diagnosing a knee sprain or strain is challenging due to the complexity of the knee. Your physician will perform a variety of physical tests, as well as take a full medical history, to determine the exact cause and location of the injury.

A patient could have multiple knee injuries at one time, so your doctor may order an x-ray or MRI. These imaging modalities will be able to identify what is causing the symptoms and help the provider determine the best treatment for your case.

Treatment for a knee strain or sprain

Many patients can self-treat knee strain or sprain with rest, ice, compression, elevation and anti-inflammatory medication. If the pain is moderate to severe, your physician may require you to wear a brace over the knee to provide stability. More advanced knee strains or sprains can be treated with the following treatments:

  • Physical therapy and rehabilitation — physical therapy is crucial to help strengthen the knee after a strain or sprain; your physical therapist will work with you to gradually add exercises that will help restore mobility in the knee.
  • PRP therapy (Platelet-rich plasma) — PRP therapy for knee strains or sprains is a newer therapy where your orthopedic physician will remove a blood sample from the patient, put the blood in a centrifuge to separate out the platelets (which contain growth factors that are important in healing injuries) and then inject them back into the patient at the affected site in the knee.

Recovery from a knee strain or sprain

It is important to work with your physician closely before you return to your everyday routine. When recovered, you should be able to perform simple exercises such as squatting, running, side to side motions and jumping without pain.

A mild sprain is healed after six weeks of resting and treating the knee. A severe strain or sprain can take as long as three to four months. The exact recovery time will depend on the treatment plan that your doctor and physical therapist recommend for you as well as the nature of the injury.

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