Knee Injections For Arthritis

What is knee osteoarthritis?

Knee joint osteoarthritis is the most common disease affecting the musculoskeletal system, seen in approx. 15% of people all over the world. The knee and hip joints, in particular, are commonly involved with osteoarthritis as they are the primary load-bearing joints within the body. Osteoarthritis of the knee refers to the wear and tear changes that result in thinning or loss of the articular cartilage. The cartilage is the protective tissue that covers the bones at the joints, and it is responsible for smooth and frictionless movement. As a result, the bones will be exposed and may rub against each other, resulting in joint pain and reduced movement. In severe cases, there might be crepitus (a grating sensation due to bone rubbing on bone), and knee joint swelling due to fluid accumulation within the joint.

What are the features of knee osteoarthritis?

The clinical features of knee osteoarthritis depend on the grade of changes and include:

-Gradual pain that usually progresses over months or years. The pain can increase in cold weather or feel more severe at the end of the day. Typically, pain and stiffness associated with knee osteoarthritis are most noticeable in the morning and feel better after warming up. It can feel worse after activities (like going upstairs and squatting). An acute flare can cause sudden severe joint pain and swelling. Pain may also be experienced at night and can interfere with sleeping.

Knee osteoarthritis pain is usually felt more at the inner aspect of the knee, as this is usually the first part of the knee joint affected by the disease. However, if the arthritis changes are significant, the pain can be widespread all over the knee and often described as a deep pain inside the knee. Please read our article about pain in the inner or outer aspect of the knee to find out more. Pain at the front of the knee could indicate changes to the patellofemoral joint (the knee cap joint).

-Locking of the knee joint, which can result from a small displaced piece of bone or cartilage that can get lodged within the joint space.

-Localised or generalised knee joint swelling

What is the best scan to assess for knee osteoarthritis?

A weight-bearing X-ray is usually helpful in determining the severity of osteoarthritis and the degree of joint space narrowing. Sometimes, more advanced imaging (called MRI) is required to provide more information about the state of the articular cartilage and the soft tissue stabilising structures in the knee.
Ultrasound is very useful in guiding intra-articular injections.

Please see our article to find out more about imaging for knee problems.

What other conditions can mimic knee osteoarthritis?

The two main conditions that can be mistaken for knee osteoarthritis are:

Patellofemoral (knee cap) pain

Meniscal tears

Knee Osteoarthritis vs Patellofemoral joint (knee cap) pain

Knee osteoarthritis is different from patellofemoral joint pain. The first causes pain, stiffness and swelling, usually at the side of the knee (usually the inner side) and mainly when performing weight-bearing activities. Patellofemoral joint (knee cap pain) usually causes pain at the front of the knee or deep to the knee cap. It is usually felt more on when going downstairs or walking downhills. Please read our article to learn more about other causes of pain at the front of the knee joint.

What is the treatment for knee arthritis?

Knee osteoarthritis treatment usually starts with physiotherapy. Some people respond very well to physiotherapy and a progressive rehabilitation program. The exercise comprises aerobic activities (walking, running, and cycling) and weight training. Younger people and people with mild or moderate degrees of osteoarthritis usually respond better to exercise and conservative management. Anti-inflammatory tablets (like Ibuprofen and Voltarol) are also helpful in managing knee osteoarthritis to help reduce the pain and inflammation associated with this condition. So, the first line of treatment usually consists of exercise/physiotherapy, weight loss, activity modification and education on arthritis.

Will I benefit from a knee joint injection for my arthritis?

An injection may be indicated if arthritis is severe and not responding to conservative treatment of knee osteoarthritis. This can be very useful in reducing pain, allowing you to undertake a rehabilitation program. One injection option is an ultrasound-guided steroid injection. This can provide rapid pain relief and is usually followed by a course of physiotherapy to utilise the window achieved by the injection to get good results with exercise and rehabilitation. Hyaluronic acid and PRP injections can provide an alternative to steroid injections and have been shown an effective treatment option for knee arthritis. They are usually used for mild to moderate knee osteoarthritis in active individuals. To learn more, please see our article about the stages of knee joint arthritis. Total knee replacements (TKR) are usually one of the latest treatment options, reserved for those with severe osteoarthritis that is not improving with injections and physiotherapy.

In ultrasound-guided knee joint injections, the ultrasound visualises the needle, guiding it accurately to the intended target. Evidence shows that this technique is significantly more accurate, less painful and produces better results than non-guided injections.

What are the available injections for knee osteoarthritis?

Ultrasound-guided corticosteroid injection

Corticosteroid (cortisone) is a well-established medicine that is routinely used to manage knee osteoarthritis. It has a strong anti-inflammatory effect that is usually very effective in reducing the pain and inflammation associated with osteoarthritis. Cortisone is usually mixed with a short-acting local anaesthetic (numbing medicine) to relieve quick pain. Many patients experience a significant reduction in knee pain and a quick return to previous levels of function after a corticosteroid injection. To find out more, please read our article about knee joint steroid injections

Ultrasound-guided hyaluronic acid injection

Hyaluronic acid can be useful in managing knee osteoarthritis, particularly mild and moderate arthritis. It has a dual role as it acts as an anti-inflammatory medication and aims to simulate the joint's natural lubrication allowing for movement in a low-friction environment. This injection technique is clinically effective at reducing pain and increasing function for patients suffering from knee osteoarthritis after just one injection for up to 180 days. Hyaluronic acid injections are not known to have adverse effects on the articular cartilage (unlike cortisone) and can be repeated every 6 months if symptoms return. To find out more, please read our article about Hyaluronic acid injections

Combination therapy

Corticosteroids and hyaluronic acid can be combined. This option provides quick pain relief secondary to the corticosteroid, with slower and longer-lasting pain relief from the hyaluronic acid (hyaluronic acid typically takes two weeks to start working). This option can be discussed with you at the time of your appointment. Still, often we prefer to start with one treatment option and assess the response or stage the injections (do a steroid injection initially to provide quick pain relief, then follow this up with a hyaluronic acid injection in about 4 weeks’ time).

Ultrasound-guided platelet-rich plasma (PRP) injections

Ultrasound-guided PRP injection involves taking a small amount of your blood, which will be spun in a special machine at high speed to separate it into different components. The plasma component can then be extracted. The plasma contains high levels of growth factors, which are very useful for tissue healing. The plasma is rich in growth factors and is re-injected into the knee joint to promote a natural healing response to the cartilage. In addition, the re-injected plasma has an additional anti-inflammatory effect to help reduce the pain and symptoms associated with osteoarthritis. There is very good evidence of the positive effect of PRP injections in treating knee arthritis. To find out more, please read our article about Ultrasound-guided platelet-rich plasma (PRP) injections

Do I need knee joint aspiration?

Knee arthritis is often associated with fluid build-up within the joint. This can be diagnosed clinically and confirmed with an ultrasound examination. Aspiration refers to the extraction of excess fluid from the knee joint, prior to any injection therapy. This is usually done at the same time as the injection procedure. The removal of knee fluid can help to increase joint movement and reduce swelling and pain. Over time, It is not uncommon for the fluid to re-accumulate within the knee after the aspiration procedure. To find out more, please see our article about knee joint aspiration.

What if injection therapy does not work?

If injection therapy and physiotherapy are not effective, then having a consultation with an orthopaedic knee surgeon is recommended. This would help to explore the other available treatment options and if there is a need for any surgical intervention.