The inability to move your hand toward the middle of your back, a motion necessary for tasks like fastening a bra or tucking in a shirt, is a common and frustrating shoulder complaint. This specific action requires a complex blend of shoulder extension, adduction, and internal rotation. Limited mobility in this arc of movement, known clinically as the Hand-Behind-Back (HBB) maneuver, often signals an underlying structural issue within the shoulder joint or its surrounding soft tissues. Understanding the mechanics behind this movement reveals why pain or stiffness in this region can severely restrict daily function.
Anatomy Required to Reach Behind Your Back
The movement of reaching behind your back relies on the high mobility of the glenohumeral joint, the primary ball-and-socket articulation of the shoulder. This motion is a multi-planar effort, combining shoulder extension (moving the arm backward), adduction (moving the arm toward the body’s midline), and internal rotation (turning the arm inward). The joint capsule, a fibrous sheath enclosing the joint, must be flexible enough to allow the head of the humerus (arm bone) to glide and rotate within the socket (glenoid).
The muscular power for this maneuver is supplied by several large and small muscles working in coordination. Internal rotation, the most restrictive component, is primarily driven by the subscapularis muscle, the largest and strongest of the four rotator cuff muscles. Extension and adduction are powerfully supported by the latissimus dorsi, the teres major, and the posterior fibers of the deltoid muscle. Any compromise to the length, strength, or function of these structures can impair the ability to perform the hand-behind-back motion.
The Role of Joint Stiffness and Inflammation
One of the most severe limitations to this movement comes from a condition called Adhesive Capsulitis, commonly known as frozen shoulder. This condition is characterized by a progressive thickening and contraction of the shoulder’s joint capsule. The capsule becomes fibrotic, meaning normal, pliable tissue is replaced with stiff, scar-like tissue, physically restricting the joint’s movement.
The classic presentation of frozen shoulder involves a global loss of both active and passive range of motion, meaning the arm cannot be moved freely by the patient or by a clinician. Loss of internal rotation is one of the most prominent signs, as the contracted capsule physically tethers the humerus, preventing the necessary inward twist for the hand-behind-back motion.
Another factor contributing to joint stiffness is glenohumeral osteoarthritis, which involves the progressive breakdown of cartilage lining the ball and socket surfaces. As the cartilage wears away, the bones may rub together, leading to pain and the formation of bony spurs called osteophytes. This narrowing of the joint space mechanically restricts the full rotation and glide required for the hand-behind-back maneuver, causing a painful internal rotation deficit.
How Rotator Cuff Damage Limits Movement
Impairment can also stem from problems with the shoulder’s active components, specifically the rotator cuff muscles and their tendons. Since the subscapularis muscle is the main internal rotator, tendinopathy (tendon irritation) or a tear in this tendon directly undermines the ability to reach behind the back. An injury results in weakness and pain when trying to initiate or sustain the internal rotation component of the movement. Patients with a subscapularis tear often report a distinct difficulty in bringing their hand away from their back against resistance, a sign of muscular failure rather than joint stiffness.
A separate issue, known as Glenohumeral Internal Rotation Deficit (GIRD), is a common concern in athletes who perform repetitive overhead motions, such as throwing. GIRD is characterized by a decrease in internal rotation range of motion in the throwing shoulder compared to the non-throwing shoulder. This restriction results from adaptive changes, including tightness in the posterior aspect of the joint capsule and the muscles that externally rotate the arm. The resulting imbalance can cause the humeral head to shift slightly, leading to pain and a mechanical block when attempting to maximize internal rotation.
Diagnosis and Treatment Pathways
Determining the precise cause of the limitation requires a thorough physical examination to differentiate between joint stiffness and muscle weakness. A clinician will assess both active range of motion (how far you can move your arm on your own) and passive range of motion (how far the arm can be moved by the examiner). If both active and passive motion are limited, a capsular issue like frozen shoulder is likely; if only active motion is limited, a rotator cuff tear or nerve issue may be the cause.
Specific tests, such as the Lift-Off or Belly Press tests, are used to isolate and assess the strength of the subscapularis muscle, indicating a potential tear. Imaging studies are often used to confirm the clinical diagnosis. X-rays can reveal the bony changes and joint space narrowing associated with osteoarthritis. Magnetic Resonance Imaging (MRI) is the preferred method for visualizing soft tissues, providing detailed images of the rotator cuff tendons and the joint capsule.
Treatment for these conditions is tailored to the diagnosis, but most often begins with conservative management. Physical therapy is a primary approach, focusing on specific stretching exercises to restore capsular flexibility for stiffness or strengthening exercises for muscle weakness. Anti-inflammatory medications or corticosteroid injections may be used to reduce pain and inflammation, particularly in the initial stages of a frozen shoulder. Surgical intervention, such as arthroscopic capsular release or tendon repair, is generally reserved for cases that do not respond to several months of non-operative treatment.