Intra-articular hyaluronic acid injection: what it is, its benefits and when it may be recommended
A hyaluronic acid injection (intra-articular injection) is a procedure used in some situations to relieve joint pain and improve mobility, especially in people with osteoarthritis or joint wear. It involves injecting hyaluronic acid, a substance naturally present in synovial fluid, directly into the affected joint.
In this article you'll learn how it works, when it may be indicated, its potential benefits, what affects the cost and how long it may take to work.
What a hyaluronic acid injection is
A hyaluronic acid injection is an intra-articular treatment that aims to improve the properties of synovial fluid, with the goal of reducing pain and stiffness. Hyaluronic acid is found in synovial fluid and helps to:
Lubricate the joint;
Reduce friction between joint surfaces;
Absorb impact during movement.
With ageing and conditions such as osteoarthritis, the amount and quality of this substance can decline. This may be linked to more friction, stiffness and pain on movement.
How the injection works
The injection is given by a doctor and involves placing the product directly inside the joint. In general, the procedure involves:
A clinical assessment;
Preparing and disinfecting the skin;
Inserting a fine needle into the joint;
Injecting the product into the joint.
It is usually a quick procedure. In many cases you can return to your activities the same day, following the doctor's specific advice. This type of treatment is often called viscosupplementation.
Hyaluronic acid in the knee: when it may be indicated
The knee is one of the most heavily loaded joints, which makes it a common site for this treatment, especially in knee osteoarthritis. The injection may be considered in situations such as:
Early to moderate knee osteoarthritis;
Persistent pain despite conservative measures (e.g. physiotherapy and therapeutic exercise, and medication when indicated);
Functional limitation when walking and in daily activities.
Benefits and limitations
The injection can help some people and, in general, the goal is to improve symptoms, not to "cure" osteoarthritis.
Possible pain reduction: by improving joint lubrication, it may reduce friction and relieve pain.
Possible improvement in mobility: some patients report moving more easily and finding daily activities easier.
A minimally invasive option: it is a procedure carried out in a clinical setting, and may be considered when other approaches are not enough or not suitable.
How much a hyaluronic acid injection costs
The cost of a hyaluronic acid injection can vary depending on:
The type/brand of product;
The number of injections recommended;
The joint treated;
Whether ultrasound guidance is used and which clinical services are included.
That is why an individual medical assessment is important before setting the plan. If you'd like to know the cost and whether it is right for you, request a clinical assessment.
How long it takes to work
In most cases the effect is not immediate. Generally, some people notice improvement within the first few days. Others may take a few weeks to feel more consistent relief. The response varies with the degree of osteoarthritis, inflammation, activity level and commitment to rehabilitation.
How long the effect of hyaluronic acid can last
In some people the effect can last several months, often between 6 and 12 months. Whether to repeat the procedure should always be decided at consultation, based on your response and a clinical assessment.
The importance of proper clinical follow-up
Joint pain should be tackled in an integrated way. In many cases, results are better when there is:
a specialist medical assessment;
physiotherapy;
therapeutic exercise;
load management, biomechanical correction and lifestyle adjustments, where applicable.
If you have pain in your knee or other joints, a clinical assessment can help identify the cause and set the best strategy.
This article and its content have been reviewed by Dr Miguel Reis e Silva, Medical Director of Sport Lisboa e Benfica, specialist in Physical and Rehabilitation Medicine, and specialist in Sports Medicine and Pain Medicine at Clínica Myalgia.
Frequently asked questions about hyaluronic acid injections
Is a hyaluronic acid injection painful?
The procedure may cause slight discomfort at the moment of injection, but it is generally well tolerated. In some cases the doctor may use local anaesthetic to minimise the sensation. Afterwards, you may feel some tenderness or temporary swelling in the treated area, which usually settles within a few days.
How many injections are needed?
The number of injections varies with the product used and each patient's individual response. Some protocols involve a single injection, while others may include a course of two to three injections a week apart. The doctor sets the most suitable plan after a clinical assessment.
Does a hyaluronic acid injection replace surgery?
Not necessarily. The injection is a conservative treatment option that may be considered before surgery, especially in early to moderate osteoarthritis. However, in more advanced cases it may not be enough, and surgery may be the most appropriate approach. That decision should always be made together with your doctor.
Are there any contraindications to this treatment?
Yes. A hyaluronic acid injection may not be suitable in situations such as active infection in the joint or surrounding skin, known allergy to the product or any of its components, and some cases of very advanced osteoarthritis. That is why a prior medical assessment is essential.
Can I exercise after the injection?
In general, it is advisable to avoid strenuous activity for the first 24 to 48 hours after the procedure. Physical activity should be resumed gradually, following the doctor's advice and, whenever possible, with physiotherapy support to optimise the results.