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  In 1934 Palmer and Meyer isolated a novel polysaccharide from vitreous of bovine eyes. It was named “Hyaluronic Acid” due to the two - sugar molecular composition, one molecule being uronic acid, and the fact that the substance derived from hyaloid (vitreous).
• In 1996 in agreement with modern nomenclature of polysaccharides the name Hyaluronan (HA) was proposed. Hyaluronic Acid, Hyaluronan, and Sodium Hyaluronate are used inter-changeably throughout the related literature.
• Hyaluronan was first marketed for human use in the early 1980s using HA derived from animal sources (rooster comb), Healon was introduced as a viscous, injectable gel for use during ophthalmic surgery. Subsequently HA has been used in many other indications, especially joint disorders.
• Hyaluronan (HA) exists naturally in all living organisms (except plants) and is a universal component of the extra cellular space .
• HA can be found in a number of body tissues including skin, the ocular vitreous body, articular cartilage (as a structural component) and synovial fluid (where it acts as a lubricant, shock absorber, metabolic medium and filter) .
• Functions of HA
  • Protecting the cartilage
    • Viscous properties - Under sheer stress (surface gliding against surface), the HA molecules in the synovial fluid act as a lubricant, protecting adjacent joint surfaces from mechanical damage.
    • Elastic properties - Under load bearing stress the HA in synovial fluid acts as a shock absorber, protecting the cartilage from compressive trauma.
  • Cartilage Nutrition
    • Small molecules such as water, electrolytes, and nutrients can diffuse to cartilage and synovium freely.
    • Larger molecules such as proteins and other inflammatory mediators encounter a higher degree of retardation in passing through the network.
  • Protecting the synovium
    • HA provides a protective barrier to the synovium as well as masking pain receptors .

• Knee Injection Technique
  • There are several ways in which the knee joint can be injected. I prefer the anterior approach .
  • With the patient lying or semi-reclining on a treatment couch, the knee to be injected is bent to 90 degrees.
  • The area around the injection site is thoroughly cleaned with antiseptic. and strict aseptic technique is used throughout.
  • Local anaesthetic is injected into the skin just to the inner side of the knee cap, and then further local anaesthetic is injected through the tissue layers to the capsule of the knee joint.
  • If there is a large joint effusion (collection of fluid), this is removed first.
  • Hyaluronic acid is then injected into the centre of the joint slowly over 15 - 30 seconds
  • The patient attends for a total of 5 treatments, ideally at weekly intervals.
  • This may not be possible in my NHS clinic, where treatment every 2 weeks may be the norm.
• Immediate effects
• • Hyaluronic acid does not have an immediate pain-relieving effect
  • You may notice a local reaction, such as pain, warmth, and slight swelling immediately after the treatment. These symptoms generally do not last long. Applying an ice pack may help to ease the pain
  • For the first 48 hours after the injection, you should avoid excessive weight bearing on the leg, such as standing for long periods, jogging or heavy lifting.
• Longer-term effects
• • Over the course of the injections, you may notice that you have less pain in your knee. Most patients notice this from the 3rd treatment onwards.
  • Hyaluronic acid does seem to have anti-inflammatory and pain-relieving properties. The injections may also stimulate the body to produce more of its own hyaluronic acid.
  • Effects may last for several months.
  • Viscosupplementation doesn’t work for everyone. There’s no proof that it will reverse or delay the progress of osteoarthritis. In addition, it’s very expensive and clinical trials have not yet proven that it is cost-effective.
  • If your current course of medication and treatment is working, stay with it. However, if your arthritis isn’t responding well, or if you’re trying to delay an inevitable surgery, you may wish to discuss this option with your orthopaedic surgeon.

• Hyaluronic acid may be injected into any synovial joint. Ostenil is the only product currently available which is licensed for use in any synovial joint.
• I have experience in treating the hip, shoulder and ankle joints.
• My practice is to inject these joints using x-ray guidance. This is because:-
  • These joints are more difficult to inject than the knee.
  • Correct placement of the hyaluronic acid can be ascertained by performing an arthrogram, which shows the correct spread of x-ray dye around the inside of the joint.
• Prior to commencing a treatment course, it is usual to perform a diagnostic LA/steroid joint injection to confirm that the cause of the pain is due to an arthritic process inside the joint.
• The same treatment protocol is then followed as for the knee joint (see table above).