Objective: The main aim of this study is to determine whether early postoperative pain is decreased when the osteotomy gap is filled with AttraX® Putty, compared to conventional open wedge osteotomy without filling the gap. The secondary aims are faster accelerated rehabilitation/regaining function, reduction of local blood loss, accelerated bone union, comparable surgical accuracy, and the occurrence of (serious) adverse events. Study design: Single-blinded, prospective, randomized controlled trial. Study population: Adult patients qualifying for open-wedge tibial, open-wedge femur or double level osteotomy. Intervention: According to a randomization scheme, the osteotomy gap will be filled with either the synthetic ceramic material AttraX® Putty or without a gap filler (conventional method). Main study parameters/endpoints: The main study endpoint is the Numeric Rating Scale (NRS) pain during the first week postoperative. The secondary study endpoints are faster rehabilitation/regaining function, reduction of local blood loss, accelerated bone union, comparable surgical accuracy, and (serious) adverse events. Nature and extent of the burden and risks associated with participation, benefit and group relatedness: Patients may have the advantage of experiencing less pain postoperatively if they are treated with the AttraX® Putty, which can contribute to a faster rehabilitation. Risks to the AttraX® Putty group may include an allergic reaction, failure to promote bone fusion and excessive bone growth. However, the preclinical studies and clinical studies show that the use of AttraX® Putty is safe for use in humans.