Nerve entrapment: Compression of a nerve that becomes trapped in a confined space due to any cause e.g. trauma, inflammation or a disease process. This usually occurs near joints. The resulting pressure on the nerve can be very painful and if left untreated can result in damage to the nerve and eventually muscle weakness and wasting. Conditions such as bone spurs, joint swelling due to injury, cysts and trauma can result in nerve entrapment. The exact symptoms will depend on which nerve is trapped and the duration and severity of the entrapment.