Hernandez NM, et al. - In a consecutive series of patients undergoing revision total knee arthroplasty (TKA) for flexion instability, researchers assessed the mean white cell count and differential profile in pre-operative aspirations of synovial fluid. They found that mean cell count and differential profile observed in patients who underwent revision TKA for flexion instability was similar to those noted in patients who underwent revision for other aseptic indications. However, in those with flexion instability, bloody serosanguineous aspirations were 6.5 times more common. This finding corroborated that many of the recurrent effusions seen in this condition are haemarthroses.