The purpose of this study is to examine the immediate effect of aerobic exercise effort on clinical and experimental pain, knee active range of motion and function in people after total knee replacement.

Total knee replacement is a prevalent orthopedic elective surgery in the Western world. After surgery, especially in the first two weeks, patients suffer from high degrees of pain that may lead to delayed recovery, increased risk to chronic pain and pain comorbidities, and may harm the knee function. In purpose to alleviate the pain, most patients tend to passive coping strategies which include the use of high levels of analgesics, including steroids, which may have accompanying side effects.

Aerobic activity is found to have a beneficial effect on pain threshold and pain tolerance in healthy subjects and in chronic pain syndromes. Researches indicate that single bout of aerobic effort increase pain threshold and pain tolerance and decrease pain severity for 15-30 minutes. Until now, the effect of a one-time aerobic effort has not been tested on subjects suffering from acute pain following surgical intervention.

This trail will examine the immediate effect of single aerobic effort on clinical and experimental pain, active knee range of motion and function among people with acute pain after total knee replacement.

40 subjects undergoing total knee replacement at the medical Center for Galilee as a result of Osteoarthritis in one of they knee, will be recruited to the study. The study will take place during the hospitalization in the 5th and 6th days after surgery. In those 2 days the subjects will participate in two meetings: in one session, the participants will be asked to perform active pedaling for 20 minutes in their upper limbs of a pulse that will be calculated approximately 60% of their maximum predictive pulse. in the second meeting the participants will perform passive training with their upper limbs for the same duration. The order of interventions will be randomly determined. Before and after the intervention, it will be examined by pain measures (pressure pain threshold, spontaneous pain perception and arousal pain by the Visual Analogue Scale (VAS) scale), at rest, in a sitting-standing-sitting transfers, while carrying an equal weight on both feet and while walking. the active range of motion of the operated knee, and functional measures - 10 Meters walk Test and Timed Up and Go test.

Inclusion Criteria:

• Candidates for unilateral total knee replacement surgery in the Department of Orthopedics 'A", at f the Galilee Medical Center.
• 18 years and older.
• Diagnosed with osteoarthritis.
• Consent to participate in the trial.
• Understand simple instructions.
• Capable of walking with walking aid independently or supervised.
• Allowed to perform medium-intensity aerobic exercise to-60% of their predicted maximum pulse.

Exclusion Criteria:

* Individuals who have a physical limitation preventing them from performing active pedaling in upper limbs for 20 minutes.