We report three athletes with symptomatic isolated ganglion of the anterior cruciate ligament. The symptoms consisted of anteromedial knee pain, worse when changing direction while running, and on squatting. All gave a history of repeated minor knee trauma without a single episode of serious injury. At day-case arthroscopy, a unilobulated cystic mass arising from a clinically and arthroscopically intact anterior cruciate ligament was noted and removed in each case. No further intra- or extra-articular knee lesion was seen. Histology revealed a cystic ganglion in each case. With early physiotherapy, the patients could start gentle training 3 wk after arthroscopy, and, at 6-month review, were fully asymptomatic. A review of the literature shows that an isolated ganglion arising from the anterior cruciate ligament is exceedingly rare, with only three such ganglia having been previously reported.