What Are the Different Types of Knee Injections?

Knee injection is performed to treat the pain arising from various knee joint diseases.

Knee injection is a procedure in which medications are injected into the knee joint to treat pain due to various causes. 

There are different types of knee injections. The most common type of intra-articular knee injection is corticosteroids.

• Steroid injections
• Infliximab injections
• Hyaluronic acid injection
• Botox (botulinum neurotoxin)
• Platelet-rich plasma (PRP) injections

Knee pain and stiffness can be debilitating and difficult to treat. Knee conditions may negatively affect the quality of life and emotional well-being.

Weight management, exercise, physiotherapy, medications, knee injections, and surgery are some approaches used to treat knee pain. 

Knee pain can result from ligament or tendon injury, fracture, cartilage loss in osteoarthritis, and inflammatory conditions such as inflammatory arthritis or septic arthritis. Knee pain can also be due to joint malalignment or dysfunction and referred pain from other areas. 

Diseases of the knee can be diagnosed based on 

• clinical presentation, 
• radiographic tests, and 
• joint aspiration (arthrocentesis). 

A knee injection is performed to treat the pain arising from various knee joint diseases. The type of medication injected and the frequency depend on the treated condition. Based on the diagnosis and extent of the disease, the doctor would recommend a treatment plan.

Knee injections are performed for a variety of reasons. Some common reasons include:

1. Pain management: Injections of corticosteroids, local anesthetics, or other pain-relieving medications can help reduce knee pain caused by conditions such as osteoarthritis, rheumatoid arthritis, and bursitis.
2. Diagnosis: Injections can be used to help diagnose the source of knee pain by injecting a dye that will help show the affected area on an X-ray.
3. Treatment: Injections can also be used to deliver therapeutic medications directly to the knee joint, such as hyaluronic acid, which can help lubricate the joint and reduce pain.
4. Inflammation reduction: Corticosteroid injections can help reduce inflammation in the knee joint, which can help relieve pain and improve joint mobility.

Indications for the various agents used for knee injections are mentioned below. 

Steroid injections

Steroid injections help to relieve pain and inflammation in individuals with:

• Osteoarthritis
• Juvenile idiopathic arthritis
• Psoriatic arthritis
• Acute monoarticular gout or pseudogout
• Rheumatoid arthritic knees

Infliximab injections

Infliximab suppresses inflammation and can be used to treat the following:

• Knee monoarthritis
• Rheumatoid arthritis
• Spondyloarthropathy (ankylosing spondylitis)

Hyaluronic acid injection

Hyaluronic acid (HA) is naturally present in the joints, eyes, and skin. HA levels decrease with age, leading to joint friction and arthritis. HA knee injections lubricate the joint, decrease friction, decrease impact, delay common aging, and reduce pain, and stiffness. HA is used in the treatment of the following:

• knee osteoarthritis 
• rheumatoid arthritis and osteoarthritis

Botox injection

• Botox (botulinum toxin) injections are not commonly used in the knee joint. Botox is typically used to treat conditions that affect the muscles, such as spasms or muscle weakness, rather than conditions that affect the joints.
• Botox injections may be used off-label to treat knee pain caused by conditions such as osteoarthritis or chronic regional pain syndrome (CRPS).
  • The idea behind using Botox in these cases is that the toxin may help to relieve pain by blocking nerve impulses or reducing muscle contractions and stiffness that contribute to knee pain.

Platelet-rich plasma (PRP) injections

• PRP is obtained from the patient’s own blood. which is processed to concentrate the platelets and growth factors. It contains growth factors that stimulate collagen formation and lubricate the joint.
  • The idea behind PRP is that the growth factors in the platelets will stimulate the body's natural healing processes and promote tissue repair. PRP can improve joint function and reduce pain.
• PRP injections have been used to treat a variety of knee conditions, including osteoarthritis, knee ligament injuries, and tendinitis. However, the effectiveness of PRP injections for these conditions is still being studied, and more research is needed to determine the long-term benefits and risks of this treatment.

Knee injection is a relatively quick procedure and may be performed under local anesthesia to avoid pain. A needle of appropriate size and length connected to a syringe is introduced into the joint and the medication is injected. Radiological guidance may sometimes be used to aid injection.  

The following is a general outline of the steps involved in a knee injection:

• Preparation: The patient's knee will be cleaned and draped to maintain an aseptic technique. The patient may also be given a local anesthetic to numb the area.
• Positioning: The patient will lie down on an exam table or x-ray table with the affected knee bent and supported by pillows.
• Imaging: Depending on the type of injection being performed, the doctor may use x-ray guidance to ensure proper needle placement.
• Injection: The doctor will use a sterile needle to inject the medication into the knee joint. The needle will be inserted through the skin and into the joint space.
• Post-injection care: After the injection, the patient will be advised to rest the knee for a few minutes and then to gently move it to help distribute the medication. Ice may be applied to the knee to reduce swelling and discomfort.

After the procedure, the patient would need to rest for a few minutes, and then they can resume normal activities. Patients may experience pain, swelling, and bruising, which resolve in a few days. Ice packs and painkillers can help reduce pain and bruising.

It's important to note that different types of knee injections may involve variations on this basic procedure, and the specifics of the procedure will depend on the individual case. Additionally, the type and amount of medication used will vary depending on the patient's condition and the doctor's specific treatment plan.

The time taken for the knee injections to work depends on the medication injected. Different medications have different durations of onset and longevity. 

• Steroids take two to three days following injection for patients to see the relief of symptoms. In the case of severe joint disease, it takes longer for the effects to begin. Steroid knee injections are usually injected three to four times a year as the effects last for 6 to 12 weeks.
• Hyaluronic acid takes three to four weeks to see the effect on pain relief after the initial injection. The effects last for two to six months, after which the injection needs to be repeated. Hyaluronic acid knee injections are typically used to treat knee osteoarthritis and can be an effective alternative to other treatments, such as oral pain medications or cortisone injections.
  • The injections are usually done in a series of three to five treatments, spaced several weeks apart.
• PRP takes longer for its action on the joints to begin, around six months, but the results are more superior and last longer than hyaluronic acid. 
• Infliximab may take a few days up to two to six weeks for the effects to begin after the first treatment. The treatment can be repeated every eight weeks.
• Botox takes three to 14 days to see pain relief and the results last for about three months.

Knee injections, including hyaluronic acid knee injections, are generally considered safe procedures. Complications are rare and are typically resolved. However, as with any medical procedure, there is a risk of complications, including: 

• Joint bleeding, swelling, and bruising: Some patients may experience pain and swell at the injection site, which typically resolves on its own within a few days.
• Damage to cartilage: In rare cases, the needle used for the injection may damage the joint or surrounding tissues.
• Infection: There is a small risk of infection at the injection site, which can be treated with antibiotics if necessary.
• Nerve damage: In rare cases, the needle may damage a nerve in the area, leading to numbness or tingling in the affected area.
• Bleeding: There may be some bleeding at the injection site, but this is usually minimal.
• Allergic reactions: Rarely, patients may have an allergic reaction to the medication or hyaluronic acid used in the injection.
• Fluid buildup: Over-injection or improper needle placement may lead to fluid buildup in the joint, known as a joint effusion.