This clinical trail will be conducted to investigate the effect of blood flow restriction (BFR) with different load levels between low blood occlusion percentage (50%) group and high blood occlusion percentage (70%) compared to moderate intensity training (60% of 1 RM) in patients with chronic knee osteoarthritis.

The main questions it aims to answer are:

1. Will there be no difference between the effect of (70% vs 50%) of BFR versus traditional moderate resistive training exercises on pain intensity in knee osteoarthritis ?
2. Will there be no difference between the effect of (70% vs 50%) of BFR versus traditional moderate resistive training exercises on quadriceps muscle strength in knee osteoarthritis ?
3. Will there be no difference difference between the effect of (70% vs 50%) of BFR versus traditional moderate resistive training exercises on rate of perceived exertion in knee osteoarthritis ?
4. Will there be no difference between the effect of (70% vs 50%) of BFR versus traditional moderate resistive training exercises on functional ability in knee osteoarthritis ?
5. Will there be no difference between the effect of (70% vs 50%) of BFR versus traditional moderate resistive training exercises on physical function in knee osteoarthritis ?

All participants will receive:

1. 16 sessions of supervised intervention 2 times per week for 8 weeks.
2. The assessment will be at 3 time points, baseline and at 4 weeks and at 8 weeks.

Knee osteoarthritis (KOA) is a prevalent degenerative musculoskeletal condition that primarily causing pain, stiffness, and disability. It is a multifactorial disease influenced by a combination of genetic, biomechanical, and environmental factors Osteoarthritis Research Society International (ORSI) recommended strength training as a possible treatment method to slow progression of knee OA. Strength training, as recommended by the American College of Sports Medicine (ACSM), must be performed at a minimum resistance training load of 60% to 70% 1-repetition maximum (1RM) for strength improvement.

Only 13% of older patients with knee OA satisfactorily can perform moderate to vigorous physical activity.

Unfortunately, risk factors of knee OA (as obesity, knee pain, knee injury/surgery) also contribute to a perceived reduced tolerance to the resistive training programs recommended for eliciting strength gains.

An alternative to traditional strength training that may be well tolerated by patients with Knee OA is Blood flow restriction (BFR) training.

This reduced blood flow creates a unique physiological environment, inducing a state of metabolic stress and cellular hypoxia in the muscles.

Although the advantages of BFRT in musculoskeletal rehabilitation that reported in the literature, there are conflicting results compared to traditional exercises, as the different protocols parameters, exercises, high risk of bias across previous studies contribute to different conclusions.

Consequently, it raises the question if BFR without exercises can be effective in comparison with traditional exercises that focus on having an efficient intensity to produce muscle strength gain.

Yet, up to authors knowledge, no study has assessed whether BFR at rest could also promote similar gains in muscle strength for the knee OA treatment, which theoretically would increase patient's adherence to KOA treatment based on conclusions of systemic review of BFR without exercises for immobilized patients after orthopedic surgery (Cerqueira et al., 2019).

Another relevant issue is the proper blood flow restriction level for optimal results. Thus, pushes the need for determining a pressure load with the least adverse effects.

Therefore, the main purpose of this study is to assess different protocols of BFR without additional exercises compared to MI-RT for pain reduction in patients with KOA. The secondary purpose is to compare two load levels (70% vs 50%) of BFRT regarding pain, quadriceps muscle strength, rate of perceived exertion, self reported physical function, and functional ability.

Inclusion Criteria:

• Patients diagnosed with chronic knee osteoarthritis referred by orthopedic surgeons participants of both genders age are 40-65.
• Patients with grade 2 and 3 OA of the knee, according to radiologic evaluation
• If both knees diagnosed as OA, the most affected one will be selected.
• Diagnosis of Knee OA who had knee pain and functional disabilities for at least three months, according to American College of Rheumatology classification at screening visit.
• Visual Analogue Scale (VAS) at rest score of ≥40 mm.
• Arabic version of the western WOMAC (ArWOMAC) scores (average 37).
• Moderate Physical activity score on the IPAQ (between 3.0 and 7.9 METS).

Exclusion Criteria:

• Moderate to significant knee synovitis
• Hot or red knee
• History and/or physical examination findings compatible with the internal derangement of knee.
• Knee pain that is initiated or increased with knee activity/exercise and finished or decreased with knee resting.
• Other muscular, articular, or neurological condition affecting lower limb function.
• Patients with any previous knee surgeries or fractures of lower limb
• Patients who had undergone arthroscopy or treatment with intra-articular hyaluronic acid during the previous 6 months.
• Psychological or psychiatric disorders that may affect a subject's participation in the study.
• Participants with congenital musculoskeletal lower limb deformity.
• Participated in other intervention studies on the past 6 months to screening
• Participants with contraindications to blood flow Restriction Training.

• The risk that sharing prevents the exploitation of the entire potential of the data obtained.
• Possible failures in patients' privacy protection.
• Technical barriers such as the lack of standard formats and possible data misinterpretation.
• Issues regarding data ownership.
• Reuse of data for unfair commercial purposes.