Basic mobility and exercise therapy without strength training following a guideline with 12 specific exercises, progressed individually.

Basic mobility and exercise therapy following a guideline with 12 specific exercises, progressed individually, and supplemented with progressive knee-extension strength training (10RM) of fractured limb every day during admission.

Basic mobility and exercise therapy following a guideline with 12 specific exercises, progressed individually, and supplemented with progressive knee-extension strength training (10RM) of the fractured limb using ankle weight cuffs, daily during hospital stay.

Maximal isometric knee-extension strength in the fractured limb in percentage of non-fractured limb. Isometric knee-extension strength will be measured using an externally fixated handheld dynamometer (Power Track II Commander; JTech Medical, Utah). A stap will be attached to the bed/chair and the patient's ankle (perpendicular to the lower leg), ensuring 90 degrees of knee flexion and an isometric contraction. The transducer will be placed under the strap at ankle level, just proximal to the malleolus, and the participant will be asked to extend the leg as forcefully as possible. Knee-extension strength will be expressed as the maximal voluntary torque per kilo body mass ([NIm]/kg), using the distance between the lateral femoral epicondyle and the center of the transducer and the body mass of each patient. The best of 4 trials for each limb will be used in analyses. The primary analysis will follow the intention-to-treat principle (last observation carried forward).

Timed Up and Go test is assessed as early as possible during in-hospital stay and at discharge.

Cumulated Ambulation Score is recorded every day from inclusion to discharge. 10 meter fast speed is assessed at postoperative day 10 and/or discharge.