2. Those referred to the orthopedic outpatient health care unit of Helsingborg hospital due to an acute knee injury by their primary health care unit will be scheduled for a clinical visit for baseline assessment (visit 1) within four weeks from their injury. To facilitate recruitment, primary care units in the local area of Helsingborg will be offered an opportunity to refer all patients with rotational knee trauma and effusion directly to the orthopedic outpatient care unit.