There is evidence to support the use of hyaluronic acid injections into the ankle joint to reduce the painful symptoms of osteoarthritis (OA). These are the results of a review of the literature performed by researchers from several universities and hospitals in Taiwan. They searched electronic databases on this topic and found nine acceptable studies over a period of 17 years. The total number of patients from the combining of the studies was 354.
Hyaluronic acid is a normal part of the matrix that makes up cartilage. It has two distinct properties that make it so important for smooth joint motion. It is both viscous (slippery) and elastic.
The viscosity allows the tissue to release and spread out energy. The elasticity allows for temporary energy storage. Together, these two properties protect the joint, help provide joint gliding action (especially during slow movement), and act as a shock absorber during faster movements.
Hyaluronic acid (HA) injected into a joint has some additional benefits. The HA replaces unhealthy synovial fluid, reduces inflammation of the synovium (lubricating fluid inside the joint), and therefore has an analgesic (pain relieving) effect. It also has a direct effect on the pressure inside the joint to separate the joint capsule where it is stuck together. Hyaluronic acid may be protective of the joint cartilage and prevent the formation of adhesions that keep the capsule from the smooth gliding action needed for normal joint motion.
With all these potential benefits, a study (like this one) to determine the true effectiveness of this treatment is important. All studies included were human clinical trials using hyaluronic acid injections into the ankle joint. Only studies of patients with painful osteoarthritis lasting more than six months were allowed. Pain was the primary outcome of interest.
After carefully analyzing the combined results from these nine studies, the authors made the following observations and recommendations:
A simple summary of this systematic review would say: hyaluronic acid injections for the treatment of painful ankle osteoarthritis may be most effective when given in the right dosage (volume and number of injections). Optimal values for dosage remain undetermined except to say that lower volume and higher number of injections seem to have the best results so far.