Studies exist which confirm that the rat is the most appropriate model for assessing the glenohumeral (shoulder) joint and its pathologies, such as osteoarthritis and disease of the tendons of the rotator muscles in the joint. However there are no recorded studies of osteoarthritis induced in the Glenohumeral Joint (GJ) in rat models, nor is there a technical protocol for the correct approach to the joint. The object of this work was to establish a technical protocol, identifying anatomical reference points which would allow correct location of the penetration site for the articular cavity of the GJ followed by simulated infiltration. Four Sprague-Dawley rats were re-used for this protocol, respecting the animal ethics principles of refinement, reduction and replacement. The anatomical reference points were established and the joint was subsequently infiltrated with Indian ink. The success of the approach was corroborated by dissection of the joint, when the Indian ink could be sighted in the articular cavity. The rat's humerus was positioned in lateral rotation, using the sternoclavicular joint as a reference and following the lower margin of the clavicle until the coracoid process and the head of the humerus were reached. The mid-line of the humerus was calculated and the ink was injected below the intersection of the inferior margin of the clavicle and the mid-line of the humerus. Successful infiltration of the joint cavity requires knowledge of the morphology of the rat's GJ and the lateral rotation movement of the humerus, following the anatomical reference points identified. This technique can be applied for induction and treatment of osteoarthritis in models.