Knot impingement after arthroscopic rotator cuff repair mimicking infection: A case report

Knot impingement as a complication after arthroscopic rotator cuff repair (ARCR) has been suggested as a cause of persistent pain with limited motion. We report on a case involving a patient who developed knot impingement after ARCR who complained of acute onset of pain with limited motion, which was confused with infection.

A 55-year-old female who complained of severe pain with limited motion of the right shoulder visited our emergency room. Passive range of motion could not be evaluated due to the patient's severe pain. The patient had undergone ARCR using a suture-bridge technique at a local clinic four months ago for treatment of a small supraspinatus tear of the right shoulder. An erosive change of the undersurface of the acromion was observed on plain radiographs of the right shoulder, and a moderate amount of bursal fluid and synovial thickening with enhancement was observed by magnetic resonance imaging. Results of an analysis of the aspirated fluid showed that the WBC count was 3960 with 90% neutrophils. The arthroscopic view showed healing of the repaired supraspinatus tendon and loose suture threads and knots with severe subacromial bursitis were observed. Debridement of inflammatory tissues of the glenohumeral joint and subacromial space was performed for the removal of all suture materials. The patient's symptoms subsided immediately after the surgical procedure.

Although the incidence of knot impingement is rare, the possibility of knot impingement after ARCR should be a consideration.