The main idea these tests probe is the health of the supraspinatus tendon within the rotator cuff. The supraspinatus is the muscle that initiates arm abduction and helps stabilize the humeral head under the acromion, making it the primary structure stressed during these maneuvers. In the empty can position, the arm is raised to about 90 degrees in the scapular plane with the thumb pointed downward (internal rotation). The examiner provides downward resistance. If this elicits pain or weakness, it suggests supraspinatus tendinopathy or a tear, because this orientation places the tendon directly under the subacromial space where impingement or degeneration commonly occurs. In the full can position, the same elevation is used but with external rotation (thumb up), which reduces impingement and better isolates the supraspinatus. A positive result here reinforces supraspinatus involvement, since the test is designed to stress that tendon while minimizing contributions from other rotator cuff muscles. These tests are not primarily used to assess the infraspinatus, subscapularis, or teres minor, which are better evaluated with tests that specifically load those muscles (for example, resisted external rotation for infraspinatus and teres minor, or bear hug/lixed tests for subscapularis).

A positive Apprehension test signals anterior shoulder instability. When the arm is placed in 90 degrees of abduction with external rotation, a positive response occurs if the patient shows apprehension or fear that the shoulder will dislocate, often with a facial grimace or guarding. Pain can accompany this reaction, reinforcing the sense of instability. This reaction reflects the patient’s perception of instability rather than a mechanical click or a laxity sign. A clunk would point more toward a labral issue revealed during a different maneuver, increased sulcus sign indicates inferior laxity, and having no pain would not meet the criterion for a positive Apprehension test.

The first metatarsal rise sign assesses the function of the tibialis posterior tendon. This tendon is the main dynamic stabilizer of the medial arch, helping to invert the foot and maintain the alignment of the hindfoot and the first ray during stance and push-off. When tibialis posterior is functioning properly, it helps keep the first metatarsal from rising as the foot plantarflexes or when rising onto the toes. If the tendon is injured or incompetent, the first metatarsal is more likely to rise due to unopposed forces acting on the first ray, producing a positive sign. Other tendons like peroneus longus, flexor digitorum longus, or extensor hallucis longus don’t play the primary stabilizing role for the medial arch and first ray in this test, so the sign specifically points to tibialis posterior integrity.

The sign detects posterior sag of the tibia, which points to a posterior cruciate ligament (PCL) injury. With the patient lying on the back and both hips and knees flexed to 90 degrees, gravity can pull the tibia backward if the PCL is compromised. A positive Godfrey’s test is when the tibial tuberosities are not level, with the tibia on the involved leg sagging posteriorly (the tuberosity sits lower) compared with the opposite leg. This posterior translation reflects loss of PCL restraint. The other ideas don’t fit: displacement on the non-involved leg would not indicate a PCL tear, end-feel changes during knee extension aren’t what this test measures, and pain with hip rotation points to a hip issue rather than a knee PCL sign.