Intra-articular hyaluronans: the treatment of knee pain in osteoarthritis.

The etiology of pain in osteoarthritis is multifactoral, and includes mechanical and inflammatory processes. Intra-articular injections of hyaluronans (HAs) are indicated when non-pharmacological and simple analgesics have failed to relieve symptoms. The HAs appear to reduce pain by restoring both mechanical and biomechanical homeostasis in the joint. There are five FDA-approved injectable preparations of HAs: Hyalgan(®), Synvisc(®), Supartz(®), Orthovisc(®) and Euflexxa(®). They all appear to relieve pain from 4 to 14 weeks after injection and may have disease-modification properties. Although several randomized controlled trials have established the efficacy of this treatment modality, additional high quality randomized control studies with appropriate comparison are still required to clearly define the role of intra-articular HA injections in the treatment of osteoarthritis.