What Are the Different Types of Knee Injections?

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

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

There are different types of knee injections. The most common type of intra-articular knee injection is corticosteroids. Other agents used are hyaluronic acid, infliximab, Botox (botulinum neurotoxin), and platelet-rich plasma (PRP).

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

Weight management, exercise, physiotherapy, medications, knee injections, and surgery are some of the 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). 

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

Indications for the various agents used for knee injections are as 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 joint aging, reduce pain, and stiffness. HA is used in the treatment of the following:

• knee osteoarthritis 
• rheumatoid arthritis and osteoarthritis

Botox injection

• Botox inhibits the sensory neurons causing pain. Hence, joint pain and stiffness significantly improve. 

Platelet-rich plasma (PRP) injections

• PRP is obtained from the patient’s own blood. It contains growth factors that stimulate collagen formation and lubricate the joint. PRP can improve joint function and reduce pain.

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.  

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 pain killers can help reduce pain and bruising.

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 relief of symptoms. In 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. 
• 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.

Complications are rare and are typically resolved. Some common complications are:

• Joint bleeding, swelling, and bruising 
• Damage to cartilage 
• Infection