The UK Knee Osteotomy Registry (UKKOR).

The orthopaedic data revolution is underway with a requirement for all orthopaedic surgeons to define the data collection culture [1]. A vehicle in this revolution are the newly emerging surgical registries, created to provide high quality, patient centred, outcome data which will be required to inform service commissioners [2]. Knee osteotomy is undergoing a separate revolution [3,4] with a resurgence of interest from surgeons looking to offer a disease modifying option for younger patients. Angular stable fixation devices now provide improved initial stability which has facilitated the increasing use of the tibial medial opening wedge [5]. Opening wedges are easier to control during the procedure offering increased surgical confidence in the achieved correction [6]. Younger patients occupy a treatment gap [7] when arthritis is graded I to III [8], because unicondylar arthroplasty is contraindicated without bone on bone contact. These patients are often told to wait until they are candidates for arthroplasty without receiving symptomatic relief. A well performed knee osteotomy can delay disease progression and treat unicompartmental arthritis with pain relief and durable restoration of function [9]. However,when compared to unicondylar and total knee arthroplasty, osteotomy has been criticised for exposure to the risks of failure and revision surgery [10]. However this reproval fails to observe the greater functional benefit from retainingnative knee kinematics and ignores that primary arthroplasties are also threatened by revision. As surgical techniques for osteotomy have evolved the previous long term follow-up studies now analyse the results of already outdated procedures [11]. Emerging papers using modern osteotomy techniques report encouraging survivorship [12]. There is clearly a requirement to provide robust evidence of patient outcomes [13] usingmodern techniques, as justification for knee osteotomy against surgical alternatives. The UK Knee Osteotomy Registry (UKKOR) has been established to provide this evidence. Clinical registries use observational study methods from a broad population base and so their findings have strong external validity [14]. The larger sample size from a registry database allows analysis of the multiple variables which can influence outcome [15]. Individual patients vary greatly in their presenting deformities and surgical techniques also vary, so UKKOR is not a registry attempting to identify outlying surgeons. Instead our focus is directed to improving the quality of patient care by monitoring outcomes. Whilst it will take