The Relative Risk of Knee Osteoarthritis after Knee Injuries - Results of a Metaanalysis

Introduction: This metaanalysis was performed to evaluate the event rate of radiological knee osteoarthritis (ER ROA) after knee injuries (minimum 10 year follow-up). Furthermore was aimed to compare the ROA after knee injury with the ROA within the normal population. Materials and methods: At deadline 28.2.2010 was performed a systematic PubMed recherche by 2 independent investigators. The search strategy was (MeSH): [knee] and [osteoarthritis] and [special injury]. Furthermore the normal ROA was evaluated for the "normal population". Criteria for inclusion were papers in German or English language, minimum follow-up and clear-defined radiological osteoarthritis grading accordingly to the Kellgren-Lawrence (KL) scale. A KL-grade of 2 + was accepted as manifest radiological knee osteoarthritis. The relative risk of ROA was calculated in fixed effect model and is expressed as relative risk (odd ratio OR (CI 95 %)). Results: A total of 1 428 publications were found as result of the search the keywords [osteoarthritis] and [knee] and prevalence]. A total of 18 publications were included in the metaanalysis. The ROA of the "normal population" without adjustment to sex or age was 27.1 (CI 95 % 26.6-27.7) %. The ROA after ACL-injury was 42.0 (CI 95% 39.844.2) %. Compared with the normal population increases an ACL-injury the ROA significantly (OR = 2.5 (CI 95% 2.3-2.7), p < 0.001). Patients after PCL-injury have a higher risk of ROA in tendency (OR= 1.3 (CI 95% 0.8-1.9), p = 0.263. Fractures near the knee joint increases the risk of ROA in tendency (OR = 1.2 (CI 95% 1.0-1.3), p = 0.05). Conclusions: Knee joint injuries are doubtless risk factors for an increased ROA. The most traumatologic outcome studies don't address the ROA. The most default of most studies is the lack of information about sex or age adjusted ROA. In future long-term follow-ups for evaluation of the age and sex adjusted ROA are needed for better understanding the progression a "post-traumatic osteoarthritis".