The sulcus sign is a specific physical examination finding used to assess joint stability. The term “sulcus” comes from the Latin word for a furrow or groove, describing the visible depression that appears when the test is positive. This sign helps medical professionals evaluate the integrity of the soft tissues surrounding the joint. Its presence indicates excessive joint movement and ligamentous laxity.
Anatomy of the Shoulder Joint
The shoulder is primarily formed by the glenohumeral joint, a highly mobile articulation often described as a ball-and-socket structure. The “ball” is the head of the humerus, the upper arm bone, and the “socket” is the shallow glenoid fossa of the scapula, or shoulder blade. This arrangement allows for an extensive range of motion but sacrifices inherent stability.
The stability of the joint relies on the surrounding structures, particularly the shoulder capsule and its reinforcing ligaments. These ligaments act like strong ropes that connect the humerus to the glenoid, keeping the ball centered in the socket. When these structures are stretched or damaged, the humeral head can translate excessively within the joint.
Eliciting the Sign: How the Test is Performed
To check for the sulcus sign, the patient typically sits or stands with the affected arm hanging relaxed by their side. The clinician stabilizes the shoulder and then applies a downward, longitudinal traction force to the patient’s arm, often by grasping the elbow. The goal is to gently pull the humeral head away from the glenoid socket in an inferior direction.
If the test is positive, a distinct groove or dimple appears in the skin just below the acromion, the prominent bony point at the top of the shoulder. This signifies that the humerus has translated downward relative to the scapula. The test may be performed in different arm positions, such as neutral rotation and external rotation, to assess various parts of the joint capsule.
Clinical Interpretation: What a Positive Sulcus Sign Indicates
A positive sulcus sign is an indicator of inferior glenohumeral instability, meaning the joint is overly loose in the downward direction. It specifically suggests laxity of the superior glenohumeral ligament and the coracohumeral ligament, which are important restraints against inferior translation. When a positive sign is present alongside instability in multiple directions (anterior and posterior), it points toward a diagnosis of multidirectional instability (MDI).
Clinicians grade the severity of the sign by measuring the distance the humeral head drops below the acromion. A common grading system uses a scale where Grade 1+ indicates a drop of less than 1 centimeter, and Grade 2+ corresponds to a drop between 1 and 2 centimeters. Grade 3+ signifies a translation greater than 2 centimeters, representing the most significant degree of laxity. This finding alone may not be pathological; a positive sulcus sign is most meaningful when the patient also reports symptoms like pain or the sensation of the shoulder “not feeling right” during activity.