[The time-related risk for knee osteoarthritis after ACL injury. Results from a systematic review]

The aim of this review was to evaluate the time-related risk for knee osteoarthritis in patients after ACL injury.

The primary search was carried out in different medical databases with the deadline 12.01.2014. The search strategy for the evaluation was [ACL] AND [osteoarthritis] including "all fields". All 1656 title/abstracts were reviewed by two independent researchers who selected 140 papers for full text review. Finally, a total of 21 relevant publications were identified for inclusion in this current paper.

The incidence of knee osteoarthritis rises significantly over time. Two years after injury it was 6.9%, after 5 years 32.2%, after 7 years 36.3%, and after 10 years 79.6%. At the same time, the crude relative risk of OA rises as the time interval since injury increases. The relative risk of OA has already doubled by 2 years after ACL injury). By 7 years it has increased fivefold and compared with OA status at the time of injury it is still increasing significantly after 10 years.

The ACL injury is a significant risk factor for the development of early-onset secondary knee osteoarthritis. Within 5 years of the injury the knee shows clear signs of osteoarthritis on MRI. However, these lesions are often not associated with any clinical signs. Knee osteoarthritis as a severe disease starts 8 years or later after the injury, when it requires treatment.