What is the Mc David PSII Hinged Knee Brace? Designed for the treatment of knee ligament injuries & cartilage tears, this hinged knee brace provides outstanding support & comfortable fit. When can I use it? For minor to moderate knee ligament & cartilage injuries & knee arthritis. Ideal for a stiff, weak or painful knee & as a rehabilitation knee brace following knee injuries. A superior design that makes it perfect for sports & skiing. What size is it? Fits left or right knee. If you are between sizes, please choose the larger size. Measure round the knee. This product can be used on either the left or the right knee. Small 30-35cm (11¾"-13¾") Medium 35-38cm (13¾"-15") Large 38-43cm (15"-17") X-Large 43-50cm (17"-19¾") XX-Large 50-56cm (19¾"-22") How does it work? This high quality knee brace features two smooth-acting, geared polycentric hinges that support the natural gliding action of the knee. Hyper-extension stops & non-slip condyle pads give a customised fit for excellent support & comfort. A nylon-faced, neoprene sleeve provides therapeutic warmth, while a sewn-in patellar buttress helps correct patellar tracking & relieves some symptoms of patella tendonitis.