Ultrasound-guided knee Hyaluronic acid injections

Intra articular Hyaluronic acid injection?

What is Intra articular Hyaluronic acid injection?

Hyaluronic acid is a naturally occurring substance within our bodies/joints. It is increasingly recognised as an effective treatment option for osteoarthritis (mainly the mild and moderate forms of the disease). The articular cartilage is a smooth structure covering the bone surface at the joints. It is responsible for the joints' smooth and frictionless movement and acts as a shock absorbent. The most internal layer of the cartilage is called the “Synovial membrane”. It lines the joint capsule and produces a special fluid within the joint (synovial fluid). This is vital for the function of any synovial joint, as it acts as a natural lubricant. The articular cartilage, including its inner layer (the synovial membrane), has a particular type of cells (called hyaluronan receptor cells). Hyaluronic acid is specifically attracted to hyaluronan receptor cells to form a semi-permeable membrane at the surface of the articular cartilage, contributing to the joint lubricant and shock-absorbent properties of the cartilage. Efficient joint lubrication depends on the viscosity of hyaluronic acid, and viscosity is directly related to its molecular weight. In other words, if the molecular weight of hyaluronic acid reduces, its viscosity also reduces. This means it will have less lubricant and shock-absorbing function, and the joint will eventually develop osteoarthritis (wear and tear changes).

In addition to the joint lubrication and shock absorbent effect of hyaluronic acid described above, it is believed that hyaluronic acid can help regulate protein synthesis and eliminate free radicals. Free radicals are usually highly reactive and unstable and can damage the joint and the articular cartilage.

Currently, Hyaluronic acid is prepared by bio-fermentation, which utilises cultures produced by certain bacteria to produce a synthetic form of hyaluronic acid.

How does intra-articular hyaluronic acid injection work?

Studies have shown that intra-articular injection of Hyaluronic acid into knee joints with osteoarthritis starts a series of reactions that result in chondral protection (protection of the articular cartilage and prevention of chondrocyte death). Also, it is found to encourage the formation of new articular cartilage and reduces joint inflammation. Furthermore, it promotes the production of proteoglycans (proteins that help build up the joint cartilage). As mentioned above, Hyaluronic acid also increases the joint lubricant and shock absorbent effect of the articular cartilage ( an effect usually referred to as viscosupplementation).

Are intra articular hyaluronic acid injections safe?

Evidence shows that hyaluronic acid injections are safe, providing longer pain relief and fewer side effects when compared to NSAIDs (non-steroidal anti-inflammatories tablets), especially for the cardiovascular and gastrointestinal systems. Research has shown that although hyaluronic acid injections result in longer-lasting pain relief compared to steroid injections, they take longer time to take effect, up to 2-5 weeks.

Does hyaluronic acid injection help with knee pain?

Yes. There is solid evidence supporting the use of Hyaluronic acid injections, particularly for knee osteoarthritis. They have a very low complications profile. There is a small possibility of increased pain (flare) is possible following hyaluronic acid injections. This can happen after a steroid injection too. Research shows that the flare-up of pain following Hyaluronic acid injections is rarer and mainly reported with repeated injections. The aetiology of post Hyaluronic acid injections pain is not clear yet. It is thought to be secondary to the accumulation of hyaluronan breakdown products within the joint, as it is mainly reported in patients who had multiple injections rather than a single one.

There is no evidence of an increased rate of local complications (infection, skin colour changes or fat atrophy) or generalised complications (anaphylaxis) when hyaluronic acid injections are compared to intra-articular steroid injections. There is good evidence showing that when these injections are done under ultrasound guidance, they are more accurate, with fewer complications and better outcomes when compared to non-guided injections.

Patellofemoral joint ultrasound guided injection

What are the different types of intra-articular hyaluronic acid injections?

Hyaluronic acid preparations currently available are either low or high molecular weight (LMW or HMW). Example brand names for HMW preparations are Durolane and Ostenil Plus, and example brand names for the LMW preparations are Ostenil and Synvisc. The viscosity of hyaluronic acid is very important to its function as it directly affects its ability to bind to hyaluronan receptors and, therefore, its effect. Different molecular weight hyaluronic acid solutions have been shown to differ in their physiological effects. LMW hyaluronic acid has been shown to have a more chondroprotective effect (protection of the cartilage) when compared to HMW hyaluronic acid. Having said that, research has shown that HMW hyaluronic acid has a more anti-inflammatory effect than LMW hyaluronic acid.

HMW and LMW hyaluronic acid preparations were reported to reduce joint pain, stiffness, and function effectively. However, LMW treatment used a prolonged course of 5 injections over 5 weeks. Another study showed a more favourable outcome when HMW hyaluronic acid was injected (approximately double the benefits). The Arthroscopy Association of Canada also recommends HMW hyaluronic acid for knee and hip osteoarthritis management. Most of the evidence we have nowadays is based on research on the effect of Hyaluronic acid injections on knee joint osteoarthritis. We believe sufficient evidence supports using hyaluronic acid injections to manage knee osteoarthritis. Both HMW and LMW hyaluronic acid injections can result in good outcomes. Overall, there is insufficient evidence to favour LMW or HMW regarding effectiveness in treating osteoarthritis. However, a single HMW injection is preferred and more convenient than multiple LMW hyaluronic acid injections.

What knee conditions are intra-articular hyaluronic acid injection useful for?

There is strong and convincing evidence regarding the effectiveness and safety of hyaluronic acid injection in the management of osteoarthritis, in particular, the knee and hip.

There is abundant evidence supporting the effectiveness and safety of hyaluronic acid injections in managing knee osteoarthritis. The current and ongoing research shows that intra-articular hyaluronic acid injections are safe and efficient for controlling joint pain, reducing the need for painkiller tablets, improving function and quality of life, and delaying surgical treatment. The effective pain relief from hyaluronic acid injections can last up to 6 months.

The most common knee conditions in which Hyaluronic acid injections can be considered are:

Summary

Hyaluronic acid is a naturally occurring substance within the joints that is essential for joint function and lubrication. Hyaluronic acid injections are an effective treatment choice for people diagnosed with osteoarthritis (wear and tear), particularly in the knee joint. Research has shown that Hyaluronic acid injections can result in a significant reduction of pain and improvement in joint function. The mechanisms of action of Hyaluronic Acid injections are multi-factorial, including chondral protection (protection of the cartilage) and thus increasing joint lubrication and shock absorption effect of the cartilage. It also has an anti-inflammatory effect and thus can help reduce the inflammation within joints. Both HMW and LMW hyaluronic acid injections can produce good results, but a single HMW injection might be preferred over multiple LMW injections.