15 years of the Scandinavian knee ligament registries: lessons, limitations and likely prospects

High-quality national health registries provide the opportunities to: (1) improve patient outcomes by giving medical units and clinicians relevant feedback about their work; (2) detect inferior treatments and (3) identify prognostic factors associated with both good and bad outcomes. The Scandinavian knee ligament registries were established in 2004 and 2005, include data from 70 000 patients,1 and have led to more than 70 studies publications already (2019). This editorial reflects on lessons learnt, limitations identified and what the future may hold. Two systematic reviews including all studies from the registries focused on factors associated with (1) additional anterior cruciate ligament (ACL) reconstruction and (2) patient-reported outcomes after ACL injury and reconstruction are summarised in table 1.2 3 View this table: Table 1 Primary findings of the systematic reviews on the Scandinavian knee ligament registries There is a balance in health registry studies between the large number of patients that decrease the type-II error (false negative) risk, and the multiple analyses and similar questions that are addressed which increase the type-I error (false positive) risk. Registry data are also susceptible to confounding interactions, some of which are unknown. Nevertheless, the registries produce results that reflect day-to-day practice owing to two key factors, a high rate of coverage (proportion of medical units who participate in relation to all eligible medical units) and completeness (proportion of target population in the registry). However, it must be remembered that the response rates from patient-reported follow-ups are a persistent challenge for health registries, where at …