Walking ALteration for Knee osteoarthritis.

INTERVENTION: Patients will be randomized in a group (a) control group: physiotherapy with a standardised treatment protocol based on the KNGF (royal Dutch association of physiotherapists) guidelines. (b) index group: WALK gait retraining program. CONDITION: Knee osteoarthritis, Conservative treatment, Knee extension deficit, Physiotherapy ; ; PRIMARY OUTCOME: Between group difference in change in pain score of the KOOS between baseline and 3 months follow‐up. SECONDARY OUTCOME: ‐ Comparison of percentage of responders according to the OMERACT/OARSI set of responder criteria, during 12 months follow up, in the control and index group. To measure pain and function, the Number Rating Scale for knee pain (NRS) and KOOS physical function will be used, while for global assessment a Likert scale will be used. These outcomes will be assessed during the first 3 months of the study: weekly, and thereafter: at 6, 9 and 12 months after baseline measurement. ; ; ; ; After 3 and 12 months of follow‐up groups will be compared concerning change since baseline of: ; ; ‐ Number Rating Scale for knee pain (NRS) ; ; ‐ EQ‐5D; Intermittent and Constant OsteoArthritis Pain (ICOAP); ; ; ‐ treatment failure (TKA during follow‐up; or in “need for TKA” OARSI‐criteria after 12 months; or other surgical interventions of the knee during follow‐up (osteotomy of high tibia or low femur; arthroscopic intervention; UKA)); ; ; ‐ Range of motion of the knee (ROM) ; ; ‐ gait parameters as assessed by gait analyses ; ; ‐ medication use. ; ; ; ; To get more insight in which specific patients will respond on the current intervention also the HADS, Central Sensitization Inventory, pain drawing form and pain cognition list will be evaluated. ; INCLUSION CRITERIA: Symptomatic knee OA according to the clinical ACR criteria. Radiographic OA, according to Kellgren and Lawrence grade 1, 2 or 3 Flexion contracture of 5 degrees or more.