During Anterior Cruciate Ligament reconstruction, using bone- patellar tendon- bone graft, debris can accumulate in the joint. We assessed incidence and potential for complications, described the radiographic appearance and defined the natural history of these intrarticular debris in 50 consecutive reconstructions. The records and radiographs of 50 consecutive cases were reviewed. A stripe of radio-opaque material, resembling a comma, termed the “comma” sign, was noted behind the lateral femoral condyle on the early postoperative radiographs of 40 of the 50 cases. There was no statistically significant difference in loss of knee motion at six, twelve, twenty- six and fifty- two weeks postoperatively (P> 0.50) between the patients presenting the radio-opacity and those without it. A second set of radiographs was taken in 12 patients between 3 and 18 months postoperatively, revealing that this radio- opaque material was visible in 1 case only. No correlation was found between presence of radio- opacities and duration of pain, effusion, analgesia requirement, discharge timing, time to driving and time to work. A protocol of postoperative early weight- bearing mobilisation had been followed in all cases which may have played a role in promoting the faster dissolution of the debris.