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Therapeutic Injections for Knee Sprains & Strains

If rest, immobilization, and in some cases physical therapy don’t offer relief from the pain of a knee sprain or strain, your NYU Langone orthopedic expert may recommend an injection of anti-inflammatory medications or a modified sample of your own blood to accelerate healing in the soft tissue of the knee.

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Our doctors sometimes recommend injections in conjunction with physical therapy to lessen pain during recovery and increase the effectiveness of therapy.

Your doctor may perform these injections in the office. NYU Langone doctors may use X-ray or ultrasound imaging to guide them during the injection process. This allows the doctor to inject the medication precisely into the knee joint, ensuring that it has the maximum effect.

Experimental injections—such as platelet-rich plasma or stem cell injections—may relieve pain and encourage healing in damaged soft tissue. You and your doctor can discuss whether you are a candidate for these injections. Though these injections are not approved by the U.S. Food and Drug Administration (FDA) to manage knee sprains and strains, doctors typically consider them safe and effective in some situations.

Corticosteroid Injection

Corticosteroids are powerful anti-inflammatory medications that alleviate knee pain and reduce inflammation. For some people, corticosteroids can provide long lasting relief when injected directly into the joint.

Typically, doctors inject a small amount of anesthetic into the knee along with corticosteroids. The anesthetic can provide immediate pain relief that wears off after a few hours, at which time knee pain may return. The corticosteroid begins to work two to three days later.


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Most people return home or to work immediately after the injection. Your doctor may recommend applying ice to your knee two or three times a day or taking an over-the-counter medication to relieve pain and reduce swelling.

Doctors recommend no more than two or three corticosteroid injections in the knee per year. If used too frequently, corticosteroids may cause side effects, including the weakening of soft tissue in the knee and skin discoloration at the injection site. Corticosteroid use can also increase blood sugar levels. For this reason, they may not be appropriate for people with certain metabolic conditions, such as diabetes.

Doctors at NYU Langone are experienced in administering corticosteroid injections and can help you to avoid the potential complications associated with these medications. For instance, if symptoms such as pain and swelling are not severe, your doctor may recommend a single injection, followed by another only if the swelling or pain returns.

Platelet-Rich Plasma Injection

If corticosteroid injections don’t provide pain relief, doctors may inject a natural substance called platelet-rich plasma into the knee to help injured tissue to heal more quickly.

Platelet-rich plasma is composed of blood cells called platelets, which are removed from your body. Platelets release substances called growth factors, which stimulate healing. In this procedure, your doctor takes a small amount of blood from a vein in your arm and uses a machine called a centrifuge to separate the platelets and growth factors from other blood components. The process takes about 15 minutes. The doctor then injects the platelet-rich liquid, called plasma, directly into the injured knee.

Our doctors use ultrasound to guide the injection. People often experience pain relief and improved function within four to eight weeks.

Stem Cell Injection

Immature blood cells called stem cells are unique in that they can develop into any type of cell, including those that help repair damaged tissue. When injected into an injured knee, stem cells may encourage a damaged ligament to heal. Stem cells also reduce inflammation. Doctors don’t know exactly how they work, but some people find that an injection relieves pain and swelling and helps speed recovery.

Our doctors obtain stem cells from your body—typically from bone marrow in your pelvic bone—using a syringe. The area is numbed before the stem cells are extracted. Next, the stem cells are separated from the blood and other substances in the bone marrow and are injected directly into the knee.

Stem cell therapy does not produce results right away. However, over time, stem cells may help damaged tissue to heal fully. Most people experience improved function and pain relief after six to eight weeks.

Recovery from Platelet-Rich Plasma and Stem Cell Injections

Doctors recommend avoiding anti-inflammatory medications, such as ibuprofen, for one week before and two to four weeks after an injection, while the knee injury heals. This is because the platelet-rich plasma or stem cell injection stimulates the body’s inflammatory response, an important part of healing that could be inhibited if anti-inflammatory drugs are taken. If the injection site is sore or swollen after treatment, doctors recommend taking acetaminophen and applying an ice pack to the area for 15 minutes, 3 times a day.

You should also avoid strenuous activities involving the knee for two to four weeks after the injection to give the injured tissue time to heal.

After four to eight weeks, your doctor evaluates the healing process. He or she may recommend an additional platelet-rich plasma or stem cell injection, depending on the extent of the injury.

Our Research and Education in Knee Sprains and Strains

Learn more about our research and professional education opportunities.