A wound on a hip can be two quite different things, and which it is changes the answer completely.
If it is a pressure sore. Hips are among the places pressure sores tend to form, where skin covers bony areas with less tissue under the skin to pad them. A hip takes the load of anyone who lies on their side, which is why side-lying is not automatically the safe alternative to lying on the back. The cause: too much pressure on the skin for too long reduces blood flow to the area, and the skin can die.
For that, what changes it is the loading. Change positions often — about every 2 hours in bed, every 15 minutes in a wheelchair. Use pillows, foam cushions, booties or mattress pads chosen with a provider. No donut-shaped or ring-shaped cushions, which reduce blood flow and may cause sores. Avoid positions that put pressure on the sore, and avoid slipping or sliding when moving.
If it is a surgical wound. Hip surgery is common, and surgical wound care applies instead. An incision sometimes breaks open, along the whole cut or part of it. A surgeon may decide not to close it again with sutures. In that case it heals from the inside to the outside, with a dressing keeping the skin from closing before the wound underneath fills in. This kind of opening (dehiscence) typically occurs 5 to 8 days after surgery.
For a surgical wound, the things to report are different: more redness or pain, swelling or bleeding, a wound that is larger or deeper or looks dried out or dark, and drainage that increases or becomes thick, tan, green, or yellow, or smells bad. And report right away a wound that has come open or stitches or staples that have come out too soon.
Either way, the general reasons apply: infection, diabetes, poor circulation, nerve damage, bone infection, being inactive or immobile, a weak immune system, poor nutrition, excess alcohol use, smoking, and a foreign body in the wound.
And the numbers. A wound that has not started to heal in 2 weeks, or has not completely healed in 6 weeks, is called non-healing. Both pressure sores and surgical wounds are among the common types treated at a wound care center.