Surgical treatment of anterior cruciate ligament (ACL) injuries are often performed with high success rates. While complication rates for a simple meniscus surgery stands at 1.5%, the rates increase up to 9% after ACL surgeries. To tackle possible complications, the risk factors have to be identified and dealt with. We will divide the risk factors into four groups, namely the severity of the injury, preoperative factors, perioperative factors and postoperative period and rehabilitation. Arthrofibrosis and infection in particular are the most troublesome complications resulting in difficult and long lasting treatment periods. It is well known that risk factors of arthrofibrosis include; preoperative limited ROM, surgical technical faults, additional collateral ligament injuries, infection and immobilization. At times arthrofibrosis can occur without any obvious risk factors, which can be associated with mediators produced as an immune system response. Another troublesome complication is septic arthritis. It is very essential to be at an alarm in suspected cases. Culture specific antibiotherapy and arthroscopic debridement and irrigation/irrigations are the main treatment options in deep joint infections.