Incidence of anterior cruciate ligament injury and other knee ligament injuries: a national population-based study

There has been an intensive research effort directed at determining the cause of non-contact anterior cruciate ligament (ACL) injury over the past decade, but few studies have reported data on the incidence of ACL and other knee ligament injury in the general population. New Zealand's no-fault injury compensation data provides a national injury resource of data on claims for knee ligament injury. The goal of this paper was to provide a descriptive epidemiology of knee ligament injury in this country. Data were obtained for knee ligament injuries between 1 July 2000 and 30 June 2005. Injuries were categorised as non-surgical (NS), ACL surgeries (ACLS) and other knee ligament surgeries (OKLS). Incidence rates per 100,000 person-years were computed using population estimates. Costs and number of treatment/rehabilitation visits were obtained as an indication of severity. The incidence rate per 100,000 person-years was 1147.1 for NS, 36.9 for ACLS and 9.1 for OKLS. Males had a higher incidence rate than females for NS, ACLS, and OKLS. The mean (and median) number of treatment visits were NS: 6.6 (4), ACLS: 27.1 (24), and OKLS: 31.3 (24). The mean (median) treatment costs of these injuries were NS $885 ($129), ACLS $11,157 ($8574), and OKLS $15,663 ($8054). Analysis of injury descriptions for ACLS injuries indicated that 58% involved a non-contact mechanism of injury. These data underscore the high level of short-term disability associated with knee ligament injuries, especially ACL injuries that require surgery.