Causes / typical injury mechanism: Rotator cuff arthropathy, also known as cuff tear arthropathy, is a condition of the shoulder that results from the progressive degenerative changes of the articular cartilage following a rotator cuff tear. Rotator cuff arthropathy is characterized by 3 features:

• Rotator cuff insufficiency
• Degenerative glenohumeral joint cartilage changes resulting in arthritis
• Superior migration of the humeral head

Classic history and presentation: This condition can present with shoulder pain that is worse at night and with activity, joint effusion, weakness, and decreased range of motion known as pseudo-paralysis.

Prevalence: This condition occurs in 4% of patients after a massive rotator cuff tear.

• Age – Often occurs in patients in their sixth and seventh decades of life.
• Sex / gender – It affects women more often than men, in a 4:1 ratio.

Risk factors: Besides older age and female sex, risk factors include smoking, increased shoulder activity, and shoulder trauma.

Pathophysiology: While the exact pathophysiology of rotator cuff arthropathy is unknown, there are 2 major theories used to explain it. The first states that calcium phosphate-containing crystals in synovial tissue induce an immunologic cascade resulting in a release of proteolytic enzymes that cause degradation of cartilage and periarticular and articular structures. The second theorizes that a massive rotator cuff tear leads to arthropathy due to mechanical and nutritional factors. Mechanically, the altered, imbalanced muscle forces lead to repetitive trauma and wear of the joint cartilage. Nutritionally, the loss of rotator cuff integrity results in the loss of quality and quantity of intraarticular synovial fluid, due to the outflow of synovial fluid from the joint leading to cartilage degradation.

Grade / classification system: In 1990, Hamada and Fukuda published a classification of the radiographic stages of massive rotator cuff tear and arthropathy:

• Grade 1 – Acromiohumeral distance greater than 6 mm
• Grade 2 – Acromiohumeral distance 6 mm or less
• Grade 3 – Acromiohumeral distance 6 mm or less with acetabularization (concave deformity of acromion under the surface)
• Grade 4 – Acromiohumeral distance 6 mm or less with acetabularization AND narrowing of the glenohumeral joint
• Grade 5 – Acromiohumeral distance 6 mm or less with acetabularization AND humeral head collapse