Opens flat for easy application over injured, swollen or tender knees. Spiral stays provide moderate mediallateral stability, yet flex and extend naturally with the joint. Opening over back of knee minimizes binding, provides additional wearing comfort. How to Measure: Measure around the bend of the knee. Size Chart X-small - knee 12.0-13.0 in. Small - knee 13.0-14.0 in. Medium - knee 14.0-15.0 in. Large - knee 15.0-16.0 in. X-large - knee 16.0-17.0 in. 2X-large - knee 17.0-18.0 in. 3X-large - knee 18.0-19.0 in. 4X-large - knee 19.0-20.0 in.