Posterior approach to shoulder aspiration or injection

When using the posterior approach for shoulder injection or aspiration, the needle is inserted perpendicular to the skin, at a point lateral to the humeral head and approximately 2 to 3 cm inferior and medial to the posterolateral corner of the acromion process. The needle is directed anteriorly towards the thyroid for injections targeting shoulder bursa or tendinopathy, or 15 degrees downward towards the coracoid process for injections targeting the glenohumeral space.