Hyaluronic acid is the "key" molecule in the biomechanics of the joints. It is a polysaccharide, an anionic, non-sulfated glycosaminoglycan (N-acetyl-D-glucosamine) alternating with D-glucuronic acid and is a substance found in synovial fluid that surrounds joints. It acts as a lubricant to allow the bones to move smoothly over each other and as a shock-absorber system to absorb joint loads.

Patients with osteoarthritis have a lower concentration and volume of hyaluronic acid in their joints than normal joints. In addition, its features are involved in the main function of synovial fluid to serve as a scavenger for free radicals and to regulate cellular activities such as protein binding. In osteoarthritis (OA) and other arthropathies, the reduction in molecular weight of endogenous hyaluronic acid greatly alters the properties of the synovial fluid, causing cartilage damage and worsening OA symptoms.

The goal of treatment with intra-articular injections of hyaluronic acid is to restore the viscoelastic properties of the synovial fluid, reducing pain and improving joint functionality by helping to synthesize proteoglycans and glycosaminoglycans with anti-inflammatory effects.

The development of biotechnology has enabled the creation of hyaluronic acids with different molecular weights.

• Low molecular weight hyaluronic acid, 500 - 730 kDa, which is the commonly used formulation. The recommended dose of intra-articular infusion is two cycles of five doses on a weekly basis, per year.
• Hyaluronic acid with an average molecular weight of 800 - 1500 kDa at the recommended dosage is two cycles of three doses on a weekly basis per year.
• Hyaluronic acid with a high molecular weight of 1500 - 3000 kDa with a recommended dosage of one dose per semester or year depending on the severity of the joint disease.

In addition to the molecular weight of hyaluronic acid, its content per dosage plays an important role. The content can range from 20mg of hyaluronic acid per 2ml to 90mg per 3ml of the formulation, certainly affecting the potency of administration. Finally, the new generation hyaluronic acids are cross-linked which can be maintained in the affected joint for a longer period, offering relief in one or two doses per year.

Hyaluronic acid intra-articular therapy can be combined with other forms of intra-articular therapies such as collagen, PRP and autologous mesenchymal stem cells. When hyaluronic acid paired with a mesenchymal stem cells have been shown to undergo chondrogenic differentiation, which leads to neo-cartilage formation and recovery of some of the degraded cartilage of patients with OA.

• Relieve joint pain
• Improving its range of motion
• Reduce joint stiffness
• Psychological encouragement of the patient since he / she can more easily participate in his / her daily activities.
• Delay of arthroplasty of the joint