We hypothesized that shoulder pain, caused by rheumatoid arthritis (RA), can lead to disuse of the affected shoulder joint. In addition to the structural changes caused by rotator cuff tears,... Show moreWe hypothesized that shoulder pain, caused by rheumatoid arthritis (RA), can lead to disuse of the affected shoulder joint. In addition to the structural changes caused by rotator cuff tears, tendonitis or synovitis disuse may play an important role in the aetiology of fatty degeneration (FD) of the rotator cuff muscles. This FD may induce proximal migration due to shoulder muscle force imbalance, causing even more pain due to subacromial impingement. FD is thought irreversible, even when the underlying pathology was treated. Early referral and treatment of shoulder involvement of rheumatoid disease may protect the rheumatoid shoulder from this downward spiral. It is of great importance to screen rheumatoid arthritis patients for shoulder joint involvement at an early stage. The use of the Upward migration Index to assess proximal migration can be used reliably to screen for the presence of rotator degeneration. In order to quantify fatty degeneration we advocate using the Mean Muscle Density measured on CT-images. We underline the importance of these measurements as they were strongly correlated to shoulder pain and functional loss. Measurement of proximal migration in an early stage can therefore play an important role in the initiation of functional and medicinal treatment of RA and may present patients with better possible outcome providing that shoulder surgery is indicated. Show less
