People often confuse shoulder impingement with frozen shoulder (adhesive capsulitis) due to shared symptoms of pain and limited arm movement. However, these are two distinct medical conditions with different mechanisms of injury, underlying causes, and specific treatment pathways. Correctly identifying the specific issue is the necessary first step toward effective recovery and regaining full shoulder function.
Understanding Shoulder Impingement
Shoulder impingement syndrome is a mechanical issue where soft tissues are compressed within the shoulder joint. This occurs when tendons, usually those of the rotator cuff, or the bursa are “pinched” as they pass through the narrow subacromial space beneath the acromion (the bony arch at the top of the shoulder blade). This structural narrowing causes rubbing, leading to inflammation (tendinitis or bursitis).
The primary cause is often repetitive overhead activity, resulting in overuse injury and progressive inflammation. Athletes and those whose work involves frequent arm elevation are susceptible. Pain is localized and worsens when the arm is lifted above the head or reaching behind the back. Discomfort subsides when the arm rests below shoulder height, as compression is relieved.
Understanding Frozen Shoulder
Frozen shoulder (adhesive capsulitis) is characterized by the stiffening and scarring of the shoulder joint capsule. This connective tissue layer thickens and contracts, physically restricting the shoulder’s ability to move. While the cause is often unknown (idiopathic), it is linked to systemic conditions like diabetes and thyroid disorders, or prolonged immobilization after injury or surgery.
The condition progresses through three distinct stages over one to three years. The initial “freezing” stage involves increasing pain and slow loss of motion. Next, the “frozen” stage sees pain potentially lessen, but stiffness plateaus, severely limiting movement. Finally, the “thawing” stage involves a slow, gradual recovery of motion and function.
How Symptoms and Movement Differ
The most significant difference lies in the nature of the pain and the shoulder’s range of motion. For shoulder impingement, pain is sharp and felt during specific movements, such as reaching overhead or across the body. Crucially, a person with impingement maintains passive range of motion; a healthcare provider can physically move the arm through its full arc, even if it is painful for the patient.
Frozen shoulder presents a stark contrast. The pain is often more diffuse, constant, and can be felt even at rest, especially during the initial freezing phase. The condition causes a severe limitation in both active and passive range of motion. The thickened joint capsule prevents both the patient and a provider from moving the arm fully in any direction. This restriction in all planes of movement distinguishes frozen shoulder from impingement syndrome.
Management Strategies for Each Condition
Treatment philosophies diverge significantly because they target different underlying biological problems. Management for shoulder impingement focuses on reducing inflammation and improving joint mechanics. This involves rest, anti-inflammatory medications, and physical therapy aimed at strengthening rotator cuff muscles to create more space beneath the acromion. Activity modification to avoid painful overhead movements is also a primary component of recovery.
In contrast, frozen shoulder management focuses on restoring lost mobility caused by capsular scarring. Treatment begins with non-surgical options like steroid injections or hydrodilatation, which involves injecting fluid to stretch the tight joint capsule. Physical therapy is intensive, focusing on stretching exercises to break up adhesions and regain movement. If conservative methods fail, surgical options such as manipulation under anesthesia or arthroscopic release of the capsule may be considered.