Anterior Knee Pain patients We will recruit 40 male adult participants who had consulted a sports medicine physician in a primary care setting for anterior knee pain complaints. A standardized history and physical examination will be conducted by the physiotherapists of the rehabilitation department for inclusion in the study.  Inclusion criteria:  age over 18 years, diagnosis of AKP confirmed by history and physical examination (with or without imaging) for more than six weeks non-traumatic history of pain onset pain at least during one of the three functional tests used as outcome measure (single-leg shallow leg squat, single-leg deep knee squat, step down) pain equal or greater than 3/10 on a numeric pain rating scale (at least in 2/3 functional tests) unobstructed knee range of motion and no pain in passive end-range knee extension  Exclusion criteria:  BMI greater than 28 systemic pathology including inflammatory joint disease or neoplastic disorders history of deep venous thrombosis hypertension (systolic pressure >140mmHg) history of endothelial dysfunction peripheral vascular disease diabetes knee pain referred from the spine history of previous neurological conditions any previous medical treatment including injections (past 3 months) or drug therapy (i.e., anti-inflammatory drugs the last 2 weeks) infection previous blood flow restriction training inability to understand written and spoken English or Arabic.  Rotator cuff related shoulder pain patients We will recruit 40 male adult participants who had consulted a sports medicine physician in a primary care setting for shoulder complaints. A standardized history and physical examination were conducted by the physiotherapists of the rehabilitation department for inclusion in the study.  Inclusion criteria:  age over 18 years rotator cuff related shoulder pain for more than six weeks pain greater than 3/10 on a numeric pain rating scale on active abduction and/or resisted external rotation at zero degrees of shoulder abduction (assessed in standing with the arm in slight abducted position)  Exclusion criteria:  full-thickness rotator cuff tear (positive drop-arm sign and/or radiographic or ultrasonographic evidence) BMI greater than 28 previous shoulder surgery or shoulder fracture imaging evidence of severe shoulder osteoarthritis or tendon calcification,\ adhesive capsulitis systemic pathology including inflammatory joint disease or neoplastic disorders restriction of passive range of motion in more than two planes history of deep venous thrombosis hypertension (systolic pressure >140mmHg) history of endothelial dysfunction peripheral vascular disease diabetes shoulder pain referred from the spine history of previous neurological conditions any previous medical treatment including injections (past 3 months) or drug therapy (i.e., anti-inflammatory drugs the last 2 weeks) infection previous BFR training inability to understand written and spoken English or Arabic