Hip and knee arthroplasties are mostly successful procedures; however, patient injuries may occur and should be reported to Löf, the Swedish patient insurance. This study investigated the incidence of patient injuries after primary total hip and knee arthroplasty in the Swedish regions, differences in incidence depending on annual surgical volume, and types of approved injuries. Approved patient injuries were related to the total number of hip and knee arthroplasties registered in the Swedish Arthroplasty Register 2012-2021. The national incidence was 11.4 and 8.1 per 1,000 hip and knee arthroplasties respectively and varied in the regions from 30.4 to 4.9 and 15.4 to 5.4 per 1,000 hip and knee arthroplasties respectively. Orthopedic departments with higher annual volumes of performed arthroplasties had a lower proportion of patient injuries. Infection was the most common patient injury, followed by nerve lesions and mechanical complications. The differences may be due to underreporting and varying quality of care in the regions. A centralization of hip and knee arthroplasties may be beneficial.