In an effort to determine the optimum solution for irrigation during arthroscopic procedures, an in vitro metabolic experiment was performed in which cartilage slices were incubated with 35SO4 in various commercially available solutions, harvested at regular intervals, and assayed for incorporated radioactivity. The solutions were compared with Ham F12 medium, a complex, ionically balanced salt and amino-acid solution that is used for tissue culture. The data show that neither normal saline or phosphate-buffered saline supports metabolic activity as well as Ringer lactate or acetate, both of which approximate the values for the control, Ham F12 solution. Clinical Relevance: Arthroscopy and arthroscopic surgical procedures have become commonplace in orthopaedic practice. Normal saline solution, commonly used in large quantities as an irrigating solution, is in fact not physiological, and we showed that it inhibits normal synthesis of proteoglycan by the chondrocytes. Ringer lactate seemed to support cartilage metabolism as well as an "ideal" tissue-culture medium (Ham F12 solution). Since Ringer solution and normal saline cost the same in our hospital, we strongly recommend that this more physiological solution be used for arthroscopic procedures.