There are different kinds of braces and uses after ACL repair. Bracing is different from the immobilizers used in the first few weeks of post-operative recovery. Some (rehabilitative) braces are used for eight to 10 weeks after the operation. The patient can then switch to a functional brace used during twisting or torquing activities.
Many studies have been done to show that bracing doesn't make a difference after ACL repair. Patients have the same long-term results with or without bracing. There's no difference in motion, strength, or endurance. The number of reinjuries later is the same with or without bracing.
Despite these findings, many patients still wear a brace for up to a year after ACL repair. This may give patients an increased sense of confidence or safety, but doesn't appear to make any real difference in function or protection.