Intra-articular steroid injection is commonly used to treat base of thumb osteoarthritis (BTOA), despite a lack of large scale data on safety and effectiveness. We estimate the incidence of serious complications and further procedures following BTOA injection, including the risk of post-operative serious surgical site infection for subsequent operative intervention.Hospital Episode Statistics data linked to mortality records from 01/04/1998-31/03/2017 were used to identify all BTOA injections undertaken in adults in the National Health Service secondary care in England. Patients were followed up longitudinally until death or 31/03/2017. A multivariable regression with a Fine and Gray model adjusting for the competing risk of mortality in addition to age, sex and socioeconomic deprivation was used to identify factors associated with progression to further procedure. Secondary outcomes included serious complications after injection and subsequent surgical site infection.19120 primary injections were performed during the 19-year period in 18356 patients. 76.5% were female; mean age 62 years (SD 10.6).50.48% underwent further procedure; 22.40% underwent surgery. Median time to further intervention was 412 days (IQR 110-1945). Female sex was associated with increased risk of proceeding to surgery. Serious complication rate following injection was 0.04% (0.01-0.08) within 90 days. Of those proceeding to surgery, 0.16% (0.06-0.34) presented with a wound infection within 30 days and 90 days, compared with an overall post-operative wound infection rate of 0.03% (0.02-0.05).Very low rates of serious complications were identified following BTOA injections performed in secondary care; only one in five patients proceeded to subsequent surgery.clinicaltrials.gov, https://www.clinicaltrials.gov, NCT03573765.