The study aims at determining the effectiveness and cost-effectiveness of surgical management of subacromial impingement (including partial tears) compared to conservative treatment. The research setting is prospective, randomised, and controlled.

The aim of the study is to search out evidence based data of indications for subacromial decompression. The investigators also aim at offering patients the most efficient and effective treatment and reduce the number of operations that do not have sufficient effectiveness. The data obtained will facilitate developing guidelines for referrals to a specialist when subacromial impingement is suspected.

The investigators hypothesise that there are subgroups of patients suffering from subacromial impingement that benefit from surgery whereas other subgroups are best treated conservatively.

Subgroup analysis:

• age
• sex
• duration of symptoms
• presence of trauma before symptoms
• presence of partial tear
• degenerative findings
• other findings in MRI or arthroscopy
• type of operation
• co-morbidities
• occupation
• pain (VAS)
• objective shoulder function
• activities of daily living

Inclusion Criteria:

• age over 35 years old
• duration of symptoms at least three months despite non-operative treatment
• accepts both treatment options (operative and physical therapy)
• must have pain in abduction of the shoulder
• must have painful arc
• must have pain in two of the three isometric tests (0 and 30 degrees of abduction, or external rotation)
• a positive result in the impingement test (a subacromial injection of lidocaine reduces pain)

Exclusion Criteria:

• previous shoulder operations
• too high risk for operation
• any disease or social problem reducing the ability to co-operate
• rheumatoid arthritis
• severe arthrosis of the glenohumeral or acromioclavicular joint
• a full-thickness rotator cuff tear in MRI arthrography
• a progressive malign disease
• adhesive capsulitis
• high-energy trauma before symptoms
• cervical syndrome
• shoulder instability