Objectives: (1) To compare level of function, activity, health-related quality of life (HRQoL) and satisfaction in persons with a lower extremity amputation before surgery and 6- and 12-months after implantation of an osseointegration implant and (2) to report adverse events. Design: Prospective cohort study. Setting: University medical centre. Subjects: A total of 40 consecutive persons (median age: 56 years) who received a transfemoral (31) or transtibial (9) osseointegration implant, between April 2014 and March 2016. Intervention: Osseointegration implant surgery followed by a predefined rehabilitation programme. Main measures: Hip abductor strength, prosthetic use, back pain frequency, postoperative pain, mobility level (Timed-Up and Go (TUG) and wheelchair-boundedness), walking ability (6 minute walking test (6MWT) and walking distance in daily life), HRQoL, satisfaction regarding the prosthesis, and adverse events. Results: Strength, prosthetic use, walking distance, HRQoL, and satisfaction level increased significantly at 6- and 12-month follow-up compared to baseline ( P ⩽ 0.002). The TUG showed no change at 6-month follow-up ( P = 0.420) but improved significantly at 12-month follow-up compared to baseline ( P = 0.005). Wheelchair-boundedness decreased from 12/40 participants at baseline to 0 at follow-ups. The 6MWT ( P ⩾ 0.038) and back pain ( P ⩾ 0.437) did not change over time. Stump pain was present in 28/39 and 22/40 of the participants at 6-and 12-month follow-up, respectively. The major adverse events were managed successfully and included three dual-cone breakages and four bone fractures. An uneventful course was completed by 19/31 transfemoral and 4/9 transtibial bone-anchored prostheses users. Conclusion: Bone-anchored prostheses lead to improved performance and appear to be safe, so they might be considered for persons with socket-related problems.