A modular knee block 10 for placing between the legs of a person when lying on a bed comprises first and second C-shaped leg supports 12, each support 12 having a medial support region 14, an anterior support region 16 and posterior support region 18 for supporting the medial, anterior and posterior sides of a persons thigh respectively. The modular knee block 10 also comprises releasable attachment means 20 for connecting the first and second leg supports 12 together, the attachment means 20 connecting the medial support regions 14. A similar device with at least two interchangeable spacers (62 figure 3, 82 figure 5), wherein the sides of the spacers (62,82) are disposed at different angles to one another for supporting the leg supports 12 to support a persons legs at the knee at an angle to one another, is claimed.
