Posterior Shoulder Instability (PSI) Classification

PSI caused by factors such as laxity of the posterior joint capsule and displacement of the humeral head can manifest as complete dislocation or subluxation.
Posterior shoulder dislocation is usually classified as acute or chronic:	Posterior shoulder dislocation within 6 weeks of trauma is acute;
	Posterior shoulder dislocation more than 6 weeks after trauma is chronic.
Posterior shoulder subluxation can be classified as traumatic or non-traumatic, with the latter further divided into voluntary or involuntary.