Adrenergic reactions could mediate metabolic and circulatory changes in the synovial membrane following knee surgery. The interstitial fluid of the synovial membrane and subcutaneous adipose tissue (reference) was monitored in vivo with microdialysis following knee arthroscopy with adrenaline added to the dialysis solvent, adrenaline together with a local anestetic added intra-articularly and without. Local metabolism and blood flow were measured. There was a similar increase, about two fold, in dialysate lactate in all three experimental conditions in the synovial membrane but no change in adipose tissue. Glucose and blood flow decreased by approximately 50% and 10% in both tissues following addition of adrenaline to the dialysate but no changes in the glucose concentrations or blood flow were observed in the other two experimental situations. As regards glycerol the addition of adrenaline caused an approximate 20% increase of the concentration in adipose tissue but an approximate 20% decrease in the synovial membrane. The intra-articular injection caused an approximate 50% increase of the glycerol level in the synovial membrane but no change in adipose glycerol. Thus, the hypermetabolic state in the synovial membrane following standard arthroscopy and the tissue damage (increased glycerol level) in the synovial membrane following postoperative pain relief by intra-articularly injected local anesthetics together with adrenaline doesn't enhance the hypermetabolic state seen postoperatively without adrenaline. However, catecholamines have pronounced in vivo effects on metabolism and blood flow in the synovial membrane.