(335) Natural history of knee osteoarthritis with regards to other joint sites and knee replacement: a population-based cohort study in the UK Clinical Practice Research Datalink (CPRD)

Background: Osteoarthritis (OA) is a clinical syndrome of failure of the joint characterised by joint pain, functional limitation, and reduced quality of life​. Among the joints, knee OA is the most common form of OA and ranks among the leading causes of disability in the elderly worldwide.

Objectives: This study aimed to describe the natural history of knee osteoarthritis (KOA) in the UK population, with regards to osteoarthritis (OA) diagnosed at other sites and with regards to occurrence of knee replacement.

Methods: The Clinical Practice Research Datalink was used to identify people with incident KOA. The survival function using Kaplan-Meier estimate will be used to analyse the time to incident OA diagnosis in other joint sites and the time to primary knee replacement following a diagnosis of KOA. Analyses will be conducted in the whole incident KOA population as well as in subgroups stratified on type of OA (primary/secondary) and presence/absence of OA in other joint sites than knee at baseline.

Results: Overall, 69% of patients have developed the knee as the first OA site. Among them, 24.2% developed a new OA site within 20 years. Spine and hip were found to be the most frequent new sites. Overall, 31.8% of patients with KOA underwent a knee replacement within 20 years. Related to the history of OA, the risk of knee replacement was significantly higher among patients with another joint with OA before KOA (HR at 2 years 1.70 [95% CI 1.64; 1.76]).

Conclusions: KOA tends to occur as the first site of an OA diagnosis. Regardless of the first OA site, KOA seems to be associated to spine and hip OA. The knee replacement will be experienced by up to third the KOA patients within 20 years from KOA diagnosis.