Posterior shoulder instability is a relatively rare phenomenon compared to anterior instability, comprising only 5-10% of all shoulder instability. Posterior instability most often occurs either as a result of high force direct trauma to the shoulder such as from a motor vehicle accident or indirect trauma such as from seizures or electrocution. Many cases of posterior shoulder instability are the result of micro-trauma that cause repetitive subluxation of the joint, ultimately compromising the shoulder in certain provocative positions. Surgical treatment of posterior instability is indicated only after an extended trial of rest and physical therapy has failed.