The purpose of this study was to investigate whether intraarticular administration of tranexamic acid could reduce hemarthrosis and postoperative pain in patients following anterior cruciate ligament reconstruction. The hypothesis of the study was that patients treated with intraarticular tranexamic acid would have significantly less postoperative hemarthrosis and less pain in the early phase of the rehabilitation process compared with those without intraarticular tranexamic acid .

Intervention Based on the previous studies, intraarticular administration with concentration of 30mg/mL was selected. The operation room nurses prepared 3g tranexamic acid in 100 mL of saline solution during operation. After finishing surgical wound suture and orthopaedic surgeons related to this study left operation room, the orthopaedic residents who were not involved in the postoperative evaluation administered tranexamic acid solution through suprapatellar pouch before tourniquet release in patients in the treatment group. The control group did not receive any solution. intraarticular drain was not inserted in all patients.

Outcome Demographic variables (age, sex, body mass index, and time from injury to surgery), clinical outcomes and surgical records including operative time, bleeding amounts, meniscus and cartilage lesions were collected by an independent orthopaedic resident. Primary outcome was a blood loss calculated based on hemoglobin balance. We assumed that blood volume in ml on the second day after surgery was the same as that before surgery. Blood volume was estimated according to the method of Nadler and colleagues taking sex, body mass and height into account. The loss of Hemoglobin was then estimated according to the formula.

Hemoglobin loss=Blood volume*(Hemoglobin concentration before surgery - Hemoglobin concentration after surgery)*0.001+total amount of allogenic hemoglobin transfused

The secondary outcome was an extent of pain measured by a visual analog scale at a consistent time in the afternoon of postoperative day 1 (PD 1) and for the next 4 day.The pain visual analog scale is a numeric response on a scale from 0 to 10, with 0 denoting no pain and 10 signifying severe pain. The other secondary outcomes included mid-patellar circumference at postoperative day 2 and day 5 and knee range of motion after 6 weeks from operation, which were measured by an independent orthopaedic fellow. The patellar circumference was measured transverse axis of the patella center to evaluate intra-articular effusion. To minimize inter-observer variance of the patellar circumference, we considered the difference between the preoperative and the postoperative results. The range of motion was documented as the extension and flexion degrees using an orthopaedic goniometer.

Inclusion Criteria:

• primary single bundle anterior cruciate ligament reconstruction using a hamstring autograft with or without meniscus surgeries

Exclusion Criteria:

• use of other grafts (allograft, bone patellar tendon bone autograft)
• revision anterior cruciate ligament reconstruction,
• concomitant knee cartilage or collateral ligament surgeries
• history of knee surgery on affected knee
• concomitant fracture
• significnat preoperative pain (Visual analoge score >5)
• coagulation or bleeding disorders
• preoperative anticoagulation treatment