Hyaluronic acid (HA) or hyaluronan (HA)

Viscosupplementation is a therapeutic procedure involving intra-articular injection of hyaluronic acid (or hyaluronan) preparations into joints—most often the knee—to restore the lubricating and shock-absorbing functions of synovial fluid that are depleted in osteoarthritis. Hyaluronic acid is a naturally occurring glycosaminoglycan that increases the viscoelasticity of joint fluid, protects cartilage, and modulates local inflammation through biochemical effects on synovial cells and chondrocytes. Commercial products include sodium hyaluronate, hylan derivatives, and various branded preparations (e.g., Synvisc, Hyalgan). Although viscosupplementation may reduce pain and improve function for several months, responses vary considerably, and procedure-related risks exist.

Other names

Viscosupplementation (procedure/therapy name)Sodium hyaluronate (salt form)Hylan (cross-linked HA product)HyaluronanSynvisc (brand name)Hyalgan (brand name)

Restores viscoelasticity and lubricative properties of synovial fluid. Reduces friction and mechanical stress in joint. Modulates inflammation by downregulating proinflammatory cytokines (IL-1β, TNF-α, IL-6). Stimulates endogenous hyaluronic acid synthesis. Inhibits cartilage degradation enzymes (matrix metalloproteinases). Promotes type II collagen and aggrecan production by chondrocytes. Analgesic effect by diminishing nociceptive signaling.