Effect of Low Intensity Training Combined With Partial Restriction of Blood Flow in Individuals With Knee Osteoarthritis

Osteoarthritis (OA) is a chronic degenerative infection that presents clinical features such as pain and limited range of motion. A weakness of the quadriceps makes this joint more susceptible to wear and tear to the articular cartilage, especially in the medial compartment of the knee. As a result, it is necessary to promote an increase of at least 30% in quadriceps strength for a beneficial effect on pain and 40% in functional capacity. Therapeutic exercises are used to increase strength muscle, in addition to high intensity exercises, to decrease joint pain, low to moderate intensity resistance training has been included, with the new approach of using partial blood flow restriction.

Physical therapy sessions will be individual and supervised, will last 30-40 minutes, twice a week, for eight weeks.

Participants will warm up with a walk or bike for 5 minutes. Then, a single series of sustained stretching will be performed for a period of 40 seconds for the following muscle groups: hamstrings, quadriceps femoris, hip abductors, hip adductors and gastrocnemius. After the stretches, active muscle strengthening exercises will be performed focusing on the quadriceps femoris muscle. The knee extension and squat exercises will be performed in four sets, with the first set being thirty repetitions or even volitional fatigue, and the following three sets will be fifteen to twenty-four repetitions, with 90 seconds of rest between each series, and two minutes of rest at the end of the four series. Both groups will perform these exercises with 30% of 1RM. The maximum load that will be lifted until volitional fatigue between 7 to 10 repetitions will be used instead of direct 1RM measurement.

Regarding the intensity of the exercises, this will be monitored by the physical therapist according to the perception of the level of effort and difficulty reported by the participant when completing the series of knee extension and squat, according to the specifications of the modified Borg scale (CR-10) . The exercises will be carried out with a load between 60-80% of the capacity and level of effort reported by the participant. The load will be increased by 2-10% when the patient is able to perform 24 complete repetitions in the last series of the exercise with perceived effort \<60%. During the exercises, a metronome will be used for the time under tension, 2 seconds for the eccentric and concentric phase.

Partial blood flow restriction will be used during knee extension and squat exercises as follows: Arterial occlusion pressure will be measured by placing a cuff on the proximal thigh in a standing position. The measurement of insufflation for each patient will be established as follows: with the participant in the supine position, the pulse of the pedal will be located with the LOGIQ e (GE Healthcare) Ultrasound. The cuff pressure will be increased until the pedal pulse can no longer be identified, and then the arterial occlusion pressure will be recorded when the pulse is restored. The RPFS will be performed at 60% of the arterial occlusion pressure for the experimental group and there will be no arterial occlusion pressure for the sham group.

Eligibility Criteria:
Inclusion Criteria:

* Confirmation of clinical diagnosis of osteoarthritis according to the criteria established by the American College of Rheumatology;
* OA knee radiograph grades 2 - 4 according to the Kellgren-Lawrence scale;
* Reporting knee pain with minimum intensity of 3 on Numerical Pain Scale;
* Complaints of pain and functional reduction in the last three months;

Exclusion Criteria:

* Diabetes type I or decompensated;
* Peripheral vascular disease;
* Uncontrolled hypertension;
* History of deep vein thrombosis;
* History of stroke;
* History of cancer;
* Cardiac pacemaker;
* Cognitive disorders;
* Neurological deficits (sensory or motor)
* Body mass index above 40 kg/m2
* Hip symptomatic osteoarthritis
* Low back pain
* Use of painkillers in the last 24 hours;
* Intra-articular infiltration with hyaluronic acid and corticosteroids in the last 6 months;
* Orthopedic surgery on lower limbs;
* Systemic inflammatory disease;
* Not able to walk