Cryotherapy has been shown to decrease intraarticular temperature in all regions of the knee after arthroscopy. The purpose of our study was to determine if similar declines in intraarticular temperature were seen with the use of cryotherapy after anterior cruciate ligament reconstruction, a procedure which, unlike simple arthroscopy, produces postoperative hemarthrosis. Sixteen patients had intraarticular temperatures measured for 2 hours after anterior cruciate ligament reconstruction with cryotherapy instituted for only 1 of the 2 hours (eight patients for the first hour and eight patients for the second hour). Significant declines were seen in the suprapatellar pouch after either hour (-2.7 degrees C in Group 1, -2.7 degrees C in Group 2) but not in the lateral gutter. The difference between cryotherapy versus no cryotherapy in the first hour in the suprapatellar pouch was 6.0 degrees C, a clinically meaningful temperature difference. We hypothesize the swelling and hemarthrosis was more pronounced in the lateral gutter because of its dependent position and therefore blunted the effect of cryotherapy seen in the lateral gutter. Cooling of the intraarticular temperature should be considered in the clinical benefits of cryotherapy.