Decubitus ulcers are lesions of the skin and the underlying tissue caused a combination of several factors. Possible causes are pressure, friction, humidity, shearing forces, temperature, age, continence, and medication. They most often occur over bony or cartilaginous areas such as sacrum, elbows, knees, and ankles.*Grade I: Non blanchable redness that does not subside after pressure is relieved. The skin may be hotter or cooler than normal, there can be edemas, or the skin may have an odd texture.*Grade II: Is damage to the epidermis extending into, but no deeper than, the dermis. In this stage, the ulcer may be referred to as a blister or abrasion.*Grade III: involves the full thickness of the skin and may extend into the subcutaneous tissue layer. The ulcer presents itself as deep, open wound, there may be undermining damage that makes the wound much larger than it may seem on the surface*Grade IV: extending into the muscle, tendon or even bone.*Stage A: wound "clean", granulation tissue, no necrosis*Stage B: wound "smeary", residual; no infiltration of surrounding tissue, granulation tissue, no necrosis*Stage C: wound similar to stage B, but with infiltration of the surrounding tissue and / or general infectionDecubital ulcer can be prevented by avoiding pressure on sensitive tissue, for example by padding, mechanical devices to mimic the effect of movement, such as alternating pressure mattresses or simply regular nursing intervention. Often a 'turning schedule' is employed to ensure the weight of the immobile patient is redistributed, reducing sustained pressure on a vulnerable area. Dehydrated people are more at risk. Also, urinary or fecal incontinence can cause skin damage and thus lead to decubitus ulcers.