Intra-Articular Injection in the Treatment of Knee Osteoarthritis

Who are the best candidates for intra-articular injection?

Dr Ang: Mild to moderate knee osteoarthritis usually respond well with hyaluronic acid (HA), platelet-rich plasma (PRP), or combination of both.

How long does an intra-articular injection last?

Dr Ang: Studies have shown that HA and PRP can last more than six months. In my practice, most patients do it annually.

Does this procedure require hospitalization?

Dr Ang: It is usually done as an outpatient or daycare procedure.

Is there any post-injection physiotherapy requirement?

Dr Ang: Usually, there will be slight swelling post-injection, and patients are advised to do regular cold pack and elevation for the first few days. Physiotherapy is helpful for osteoarthritis in terms of pain relief, reduce stiffness and thigh muscle strengthening.

Intra-articular injection is a steroid. Any side-effects?

Dr Ang: Intra-articular steroid injection can provide an excellent anti-inflammatory effect. It is usually done for acute exacerbation of osteoarthritis or inflammatory arthritis like rheumatoid arthritis and gouty arthritis. Since it is injected into joint space, systemic absorption into the bloodstream is minimal to cause systemic side effects. However, studies have shown multiple times injections of steroid in the long term can cause further cartilage thin out.

Is age a factor in considering intra-articular injection as an alternative to TKR?

Dr Ang: Yes. For a patient who is too young for TKR, or elderly who has multiple medical co-morbidities who is unfit for surgery.

Older adults often have complex and multiple disorders. As a surgeon, how do you view your challenges in improving the quality of life of older people?

Dr Ang: TKR is proven to improve the quality of life of knee osteoarthritis patient. However, every surgery carries certain risks and possible complications, especially in elderly who has multiple medical co-morbidities. Recent medical advancement has allowed pretty decent control over multiple chronic disorders, improvements in surgical techniques, advancement in materials, and instruments have lead to shorter operation time, less bleeding, lower infection rates. Better implant design improves longevity and addresses osteoporotic bone in elderly. In general, post-operation recovery is faster, and shorter rehabilitation process has reduced other risks like deep vein thrombosis, improve surgical outcomes and implant longevity, and subsequently better quality of life. In my practice, if medical co-morbidities are reasonably controlled, and surgical benefits outweigh the risks, surgery is still my preferred choice of treatment.

Are there any restrictions for doing an intra-articular injection?

Dr Ang: Generally, if there is active knee infection, the injection should not be given. In my practice, do not give HA/PRP during acute exacerbation of arthritis except steroid to avoid excessive swelling and pain. The injection should not also be given if the patient is allergic to the component of HA /PRP.

Are the options and the personal goals of the patient discussed in arriving at the best treatment?

Dr Ang: Good clinical practice should always explore patient expectations before the commencement of any treatment plan. Current evidence does not suggest intra-articular injection as a cure for knee osteoarthritis. It is merely an adjunctive to ease symptoms and functions. There are still non-invasive and non-pharmacological options available like weight reduction, activities modification, low impact exercises, applying topical NSAIDs, rest, walking aid and oral pain killer during bad days etc., and of course a more proven treatment method, TKR.

In my practice, patients are always informed regarding the effectiveness of intra-articular injection, which may not last long, or it may not be effective at all before they consented for the procedure. Available options are always discussed at the same time.

Can you tell us about platelet-rich plasma use in intra-articular injection?

Dr Ang: Platelet-rich plasma or PRP, a mixture of high concentration of platelet and associated growth factors, derived from the centrifugal separation of patient own whole blood or other persons whole blood. It is injected into the knee joint in the hope of promoting healing in wear and tear joint. More and more studies have shown promising outcomes of PRP, especially in younger patients. However, further studies still needed to determine the details like optimum preparation methods, volumes, concentration etc.

The key symptom of knee osteoarthritis is pain. What are the options available with intra-articular injection in minimizing this pain?

Dr Ang: Hyaluronic acid (HA), is the natural collagen in our connective tissue. The function is providing cushioning, lubricating and viscous effects in knee joints. HA injection or viscosupplementation is to replace or supplement the progressive loss of HA in osteoarthritis knee. It can be avian derived or produced via bacteria fermentation. The higher molecular weight variant (more than 1 million Dalton) is shown to be more effective. It is also shown to be more effective when used in combination with intra-articular steroid.

Intra-articular steroid injection is very effective in treating the pain during acute exacerbation of osteoarthritis or inflammatory arthritis like rheumatoid and gouty arthritis.

Intra-articular stem cell injection. The mesenchymal stem cell is used in intra-articular knee injection with the hope that stem cell will proliferate and differentiate into cartilage to replace and repair the damaged host cartilage. These cells are usually sourced from patient own bone marrow aspirates, adipose tissue, or peripheral blood. Although many active studies are ongoing, there is still no strong evidence to suggest the stem cells as a cure to osteoarthritis. In fact, there is still a lot of debate going on regarding its efficacy, cell harvesting, processing, characterization and delivery.

In intra-articular injection, are there any risks that might overshadow their potential benefits?

Dr Ang: Although it is a minimally invasive outpatient procedure, but a small risk of introducing infection into the joint cavity still possible. It may cause skin redness, skin irritation over the injection site, especially avian derived HA if the patient is allergic to avian products.

What about the recovery and regain process after the intra-articular injection?

Dr Ang: Most patients will have some knee swelling post-injection which may last a few days, but they are generally able to walk independently immediately after injection. They are advised to use a cold pack and elevate the knee when at rest. It is not advisable to receive this treatment too near to their planned trip or vacation.

What are the current challenges in intra-articular injection for the treatment of knee osteoarthritis?

Dr Ang: Efficacy of intra-articular injection is not consistent, and a lot of time is short-lived. We do not know exactly which patient will respond well even though they are in the same stage of the disease. We also do not know how long it will last. Intra-articular injections are still not a cure to osteoarthritis as none of them have shown to replace or to regenerate cartilage especially in advance stage of osteoarthritis and also in the elderly who usually do worse when it comes to tissue regeneration capacity.