Knee pain, whether caused from injury or degenerative conditions such as osteoarthritis, often lingers and can be difficult to fully eradicate. Fortunately, doctors have at their disposal a variety of pain relieving methods that don’t involve surgery, yet are effective at helping people regain full mobility while reducing discomfort. If you suffer from pain, an injection for knee pain could help relieve your pain and help you get back to your life.
What is an injection for knee pain?
With any type of machine, the longer you use it, the more stress and strain is placed on its moving parts. This holds true with our bodies as we age. A common feature of aging is osteoarthritis, especially in the knee. Osteoarthritis affects our joints and is seen as a “wear and tear” condition that is simply a function of our joints being used repetitively for a long period of time. We feel osteoarthritis most keenly in our weight-bearing joints.
The following videos covers the other causes of knee pain, which can include injury or other degenerative conditions.
There are many different types of treatments for knee pain. A common procedure after you have attempted rest, ice, and non-steroidal anti-inflammatory drugs (NSAIDs) is to get an injection for knee pain. There are a few different types, including:
- Corticosteroid injections for knee pain (the most common type, especially for osteoarthritis)
- Hyaluronic acid injections
- Platelet rich plasma injections
- Medial branch blocks
A cortisone shot is just one type of knee joint injection, even if it is the most common. Others may include hyaluronic acid (HA) or platelet rich plasma (PRP). HA injections are generally aimed at restoring lubrication in the knee joint. PRP works to use the patient’s own red blood cells to repair damage. If you are considering any type of knee joint injection, here’s what to expect.
What is a corticosteroid injection for knee pain?
Injecting corticosteroids directly into the knee is a highly effective way of treating knee pain. These injections are commonly used to treat pain and any possible swelling that stems from osteoarthritis, a condition that develops when the knee’s cartilage wears down, resulting in pain and inflammation.
Corticosteroids are drugs that resemble cortisol, a hormone widely found in the body. Because of this, you may hear this injection for knee pain referred to as cortisone or corticosteroid injections. These steroids differ from those athletes take to enhance performance. Instead, the injections work by depressing the immune system’s inflammatory response, which helps to reduce pain. This inflammation is caused by the rubbing of bone on bone in the knee joint. Rubbing occurs in the joints as cartilage naturally wears thin over time.
Conditions treated with a corticosteroid injection
Osteoarthritis is the most common source of knee pain, but there are other conditions that can affect this complex joint. Four bones make up the structure of the knee: the patella, fibula, tibia, and femur. Cartilage and ligaments connect all of these bones and keep them stable.
The posterior and anterior cruciate ligaments (the PCL and ACL) connect at the center of the knee joint and help stabilize the knee through rotation. The lateral and medial ligaments also help stabilize and support the joint, while the medical meniscus cartilage provides cushioning.
Damage, injury, or deterioration in any part of this joint can cause knee pain. In addition to pain caused by osteoarthritis, some of the most common pain conditions treated with a cortisone shot in the knee include:
- Cartilage tear
Each of these conditions causes inflammation, pain, and limited mobility.
The injection for knee pain procedure
Before any treatments occur, a pain management specialist will take a complete medical history. A thorough physical examination that includes range-of-motion tests will be conducted.
In some cases, the doctor may request imaging such as X-ray or MRI to confirm a diagnosis. A cortisone shot in the knee may not be the first treatment offered if the pain is mild and can be managed in other ways. If an injection for knee pain is recommended, the knee will be thoroughly cleaned and sterilized. A local anesthetic is used most often, but patients may request mild sedation if that is more comfortable.
The pain management specialist uses fluoroscopy (live X-ray) to guide a very thin needle into the joint space of the knee. Proper placement of the injection is important for both patient safety and pain relief. Once located, a corticosteroid is injected into this space.
The entire procedure takes between 15 and 30 minutes. In many cases, pain relief is dramatic and occurs within 24 to 48 hours. Patients need only take minimal time off (usually just the day of the procedure).
Due to potential long-term side effects, these shots are best used for occasional relief or to help patients persevere through painful osteoarthritis flare-ups. Doctors typically only recommend patients receive two to three shots at most per year. Receiving shots too frequently could damage the body’s ability to regenerate knee cartilage, compounding damage already present from osteoarthritis.
The following video shows this procedure taking place live.
Effects from knee corticosteroid injections
A corticosteroid injection for knee pain is most effective for the first shot, with its pain-relieving effects diminishing slightly with each shot after. The effects of a shot can last from four to six weeks. Results can be improved if other lifestyle and supportive changes are made to manage knee pain.
Corticosteroid shots will not be injected directly into a tendon. If the pain management specialist believes that an inflamed tendon is the cause of pain, they may choose to place the injection near the tendon instead.
Potential side effects
Although a corticosteroid injection for knee pain is minimally-invasive and non-surgical, there is a slight risk of side effects. Side effects are rare and generally mild. Short-term, less serious side effects can include:
- Swelling, pain, or bruising at the site of the injection
- Allergic reaction
- Face flushing
- Synovium inflammation
- Temporary increase in blood sugar
Over time and with more injections, side effects can become more prevalent and serious. Tendons and cartilage may become weaker. Other long-term side effects of cortisone shots in the knee are:
- Easy weight gain and puffiness
- Easy bruising
- Thinning skin
- High blood pressure
- Increased risk of osteoporosis
- Bone damage (avascular necrosis or osteonecrosis)
Does it work?
Finally, you want to know if it works. A meta-analysis of high-quality studies in the UK found that a corticosteroid injection for knee pain was effective for relieving inflammation and pain in both the short and long term. The analysis also found that although there is concern for cartilage damage due to the corticosteroids, most cases of damage were due to the underlying disease, not the shot in the knee.
Another study compared the results of knee injections versus placebo groups and found clinical and statistical evidence that a corticosteroid injection for knee pain offered more pain relief at one week than placebo.
Finally, a meta-analysis in 2015 looked at all types of treatments for knee pain and found that a cortisone shot in the knee was the most effective. This meta-analysis included 137 studies with over 33,000 study participants total. The focus was on short-term pain relief, with the reviewers noting that long-term data is not robust enough to include.
What is a hyaluronic acid injection for knee pain?
Another type of injection useful for treating knee pain is hyaluronic acid. This naturally occurring substance is found in healthy knees and other joints. It provides lubrication, ensuring the joint fluidly glides without friction, and also helps with cushioning.
However, when people develop osteoarthritis in the knee, the hyaluronic acid thins and provides less lubrication and cushioning, which contributes to overall pain. Shots of this important lubricant are available to mitigate the problem.
The shots need to be administered more frequently than corticosteroid shots to be effective. Patients typically receive hyaluronic acid injections one per week, over the course of three to five weeks. Results generally take longer to notice, too.
Side effects from hyaluronic acid are minimal. Additionally, the shots may help slow down the progression of osteoarthritis by providing the knee with appropriate lubrication and cushioning, according to Arthritis Today.
Does it work?
A review of studies conducted by researchers at the University of Queensland found patient relief took about five weeks to reach full impact, and peak pain reduction lasted around three months. Reported pain levels dropped anywhere from 28% to 54%. The ability of those studied to move and engage in daily activities without interruption from osteoarthritic knee pain also improved anywhere from 9% to 32%.
Some people experience greater relief with the shots than others, reports Arthritis Today, with about 30% of patients reporting near total pain elimination for up to two years. Conversely, about 20% of people find the shots don’t offer any relief at all. Researchers still aren’t sure what factors make someone a prime candidate for a hyaluronic acid injection.
What is a platelet rich plasma injection for knee pain?
Injections of platelet rich plasma (PRP) are frequently used to treat knee pain resulting from sprains, chronic tendon issues, or osteoarthritis. The process involves injecting a patient with a special preparation made from his or her own blood.
Blood contains platelets that help to clot blood, but also contain growth factors that promote healing from injuries and decrease inflammation. To create PRP, a doctor initially draws blood from a patient. Then, the doctor separates the blood’s platelets from the rest of the plasma using a special piece of equipment called a centrifuge, which spins the blood around at a high speed. The force of spinning separates the platelets from the rest of the blood.
Once the platelets are separated, the doctor injects them into the patient’s knee.
After the procedure, patients must rest and then usually begin a physical therapy program. During this time, the PRP works inside the knee to promote healing. Sometimes, additional treatments are required to achieve pain reduction.
A study conducted by New York City’s Hospital for Special Surgery found PRP slowed the progression of knee osteoarthritis in up to 73% of people. The procedure is relatively safe, but complications may include infections, nerve injuries, or tissue damage.
How do medial branch blocks for knee pain work?
Finally, this procedure is another that focuses on a potential root cause for knee pain—the spine. Medial branch blocks are performed by injecting medication into the spine’s facet joint, which connects the vertebrae to one another. The medication, a steroid or similar-acting substance, targets the nerves responsible for radiating pain through the knee.
The injection blocks nerves in the spinal column from spreading pain signals to the knee. If the treatment works, patients may experience pain reduction for anywhere from 12 to 18 months.
What should you do?
In all of the research above, researchers are careful to note that an injection for knee pain may address the symptoms of pain and inflammation in the short-term but underlying causes must be addressed for proper treatment. A knee joint injection, most importantly, may allow you to begin other treatments, such as physical therapy, so that a holistic pain management plan can be implemented.
If you’re ready to learn more about an injection for knee pain, click below to talk to a PainDoctor.com certified doctor in your area. They can suggest the best treatment options for your pain, as well as how an injection could help.