Mylène Jansen

12 Chapter 1 aged 65 or younger. 25 It is therefore of paramount importance that placement of a knee prosthesis is postponed in these young patients with joint-preserving treatments. In case OA primarily affects only 1 compartment of the joint combined with varus or valgus leg axis deviation, (high) tibial or (low) femoral osteotomy can be applied, which (over)correct the leg axis, relieving the affected compartment. 26,27 A joint-preserving technique that can be used in uni- and bilateral OA is knee joint distraction (KJD). In joint distraction, the 2 bony ends of a joint are temporarily (6–9 weeks) placed at a certain distance (generally 5 mm), using an external fixation frame. 28 Following successful application of ankle distraction for ankle OA, KJD has been applied in several clinical trials and even in regular care conditions in a limited number of Dutch hospitals, focusing not only on symptom relieve but on cartilage regeneration as well. Although the exact working mechanism of the treatment is not yet clear, more and more details of the underlying processes are being revealed. Aim and outline thesis Many previous PhD theses have laid the foundation and brought KJD to where it is at present, from dissertations by Van Valburg in 1997, Marijnissen in 2001, and Intema in 2010 on joint distraction, to those by Wiegant in 2015, Van der Woude in 2016, and Besselink in 2018 specifically on KJD. 29–34 Most of the work in this thesis builds on that foundation, aiming to take the next steps and moving forward with KJD, in 2 directions. Part I focuses on clinical outcome and patient experience after KJD treatment. In chapter 2 , an overview of the current literature reporting on the benefit of KJD is given in a systemic manner. Chapter 3 describes on the first long-term results and clinical success of KJD treatment in an open prospective study. In chapter 4 , KJD is compared with 2 alternative treatments, HTO and TKA, 2 years after treatment in 2 RCTs. Subsequently, return to sport and work 5 years after treatment is compared between KJD and HTO in chapter 5 . As successful treatment in these clinical trials led to KJD being applied in regular care, in chapter 6 clinical outcome in regular care is evaluated and compared with data obtained from clinical trials. Since all patients thus far were treated with a device not specifically intended for KJD, a dedicated device was developed, and its user-friendliness in clinical practice was evaluated in chapter 7 . The use of cadexomer iodine ointment during KJD is reported on in chapter 8 , to further improve user- friendliness and patient experience. In chapter 9 , the 1-year follow-up results of the dedicated device are evaluated in an interim analysis from a currently ongoing prospective study. Part II focuses on processes and potential working mechanisms occurring inside the joint as a result of KJD treatment. Chapter 10 provides an overall picture of KJD, from clinical evidence to molecular mechanisms. Before specifically discussing the different joint processes, the