Glenohumeral Internal Rotation Deficit (GIRD) is a common shoulder condition seen in athletes who perform repetitive overhead movements. It involves a loss of mobility in the shoulder joint, disrupting the arm’s natural motion. GIRD is a specific change in the shoulder’s range of motion that often leads to pain and decreased performance. Understanding this deficit is key to effective management and prevention.
Defining Glenohumeral Internal Rotation Deficit (GIRD)
GIRD is defined by a measurable loss of internal rotation in the glenohumeral joint of the dominant arm compared to the non-dominant arm. The glenohumeral joint is the primary ball-and-socket joint of the shoulder, formed by the head of the humerus and the glenoid cavity of the scapula. This joint is responsible for the wide range of motion necessary for overhead activities.
The deficit is measured by comparing the range of motion of both shoulders while the arm is abducted (lifted away from the body). Clinically, GIRD is often diagnosed when there is a loss of internal rotation of 20 degrees or more. This limitation is frequently accompanied by an increase in external rotation in the same shoulder, known as an adaptive change.
A comprehensive assessment focuses on the total arc of motion, which is the sum of internal and external rotation. Pathologic GIRD occurs when the loss of internal rotation significantly reduces the total arc of motion. The mechanical cause of this loss is the tightening and thickening of the posterior capsule, a band of connective tissue encasing the joint.
Primary Causes and Affected Populations
GIRD is primarily driven by the repetitive, high-velocity demands of overhead sports, such as pitching, tennis serving, and volleyball spiking. This constant, forceful motion repeatedly stretches the anterior shoulder structures while placing intense load on the posterior structures.
This repeated stress causes adaptive changes in the soft tissues. The posterior capsule, which stabilizes the back of the shoulder, tightens and thickens over time in response to the strain. This tightening mechanically limits the arm’s ability to rotate inward.
The most affected populations are overhead-throwing athletes who train frequently, especially baseball pitchers. Other high-risk athletes include javelin throwers and competitive swimmers. These athletes may also develop humeral retroversion, a bony change that increases external rotation while reducing internal rotation.
Recognizing the Signs and Functional Limitations
Individuals developing GIRD often first notice subtle changes in their overhead performance. A common complaint is a deep ache in the back of the shoulder that worsens after prolonged activity. Athletes frequently report stiffness, requiring an extended warm-up period to achieve adequate mobility.
A significant functional limitation is the “dead arm” feeling, marked by a sudden drop in throwing velocity or power. Daily movements may also be restricted, such as difficulty reaching across the body or rotating the arm inward. Pain may also occur during the follow-through phase of a throwing motion.
GIRD alters normal shoulder biomechanics, increasing the risk for secondary injuries. Restricted internal rotation forces the head of the humerus to shift forward and upward during overhead motion, causing abnormal contact with other structures. This abnormal joint movement can lead to injuries like superior labral tears (SLAP lesions) or rotator cuff tendinopathy due to internal impingement.
Management and Rehabilitation Strategies
The standard management for GIRD is non-surgical, focusing on restoring lost internal rotation through targeted stretching and physical therapy. The primary goal is to regain flexibility in the tight posterior capsule of the shoulder. A professional assessment by a physical therapist or sports medicine physician is necessary to accurately measure the deficit and tailor the treatment plan.
Targeted Stretching Exercises
The “sleeper stretch” is a specific exercise widely used to target the posterior capsule. This stretch is performed while lying on the side of the affected shoulder, with the arm bent 90 degrees away from the body. The individual uses the opposite hand to gently push the forearm toward the surface, inducing internal rotation until a stretch is felt in the back of the shoulder. This stretch should be held for a set duration and repeated multiple times daily, often at various angles of arm elevation.
Another effective exercise is the cross-body stretch, where the affected arm is pulled across the chest with the opposite arm to stretch the posterior shoulder. To ensure the stretch focuses on the joint capsule, the individual must avoid allowing the shoulder blade to lift off the back. These stretching exercises are typically performed during the acute phase of rehabilitation to normalize range of motion.
Strengthening and Prevention
For long-term management and prevention, stretching is combined with strengthening exercises to correct muscle imbalances. Strengthening the internal rotator muscles, such as the subscapularis, helps counteract the overdeveloped external rotators common in overhead athletes. Focusing on scapular stabilizers, including the serratus anterior and trapezius, improves shoulder blade control and stability, which is necessary for proper overhead mechanics.