## 1 Introduction  
Osteoarthritis (OA) is a common and debilitating whole-joint disease affecting millions of people worldwide [1]. For knee osteoarthritis (KOA), the prevalence is estimated at around 23% in people aged over 40, which is expected to increase due to aging, obesity, and the lack of disease-modifying OA drugs [2]. Furthermore, this whole-joint disease has various personal, social, and economic consequences for patients, their environment, and society. While there are a variety of possible treatments for KOA involving braces, exercise therapy, oral or topical non-steroidal anti-inflammatory drugs, intra-articular injections, and total knee arthroplasty (TKA), it can be stated that not every patient benefits from a similar intervention [3]. While TKA is a common and effective treatment for KOA, especially in the elderly with typically higher Kellgren-Lawrence scores, it is found less suitable for younger, more active patients [4]. As the decision for TKA strongly depends on the patients' remaining functionality, quality of life (QoL), and structural degradation, surgery is often not the preferred method of treatment at the onset of KOA [5, 6]. Nevertheless, a significant amount of time is often spent with a diminished QoL, while aiming to maintain a certain level of physical activity, albeit accompanied by pain, discomfort, and frustration. To tackle these problems and improve the QoL, many of these patients might benefit more from customized exercise therapy, infiltrations, and weight loss in order to maintain a healthy lifestyle and reduce work abstinence while postponing primary TKAs and preventing revision TKAs, thus simultaneously reducing the social economic burden [3; 7; 8]. As supervised exercise therapy has proven to be effective in tackling pain and disability caused by KOA, it is often promoted as the first line of treatment [3; 7; 8; 9]. Within the relatively young KOA population, the need for customized exercise therapy to strengthen the lower limb muscles and prevent the weakened joint structures from being loaded excessively is indisputable. By improving muscle force and patient function, respective exercise therapy can improve the patient's QoL substantially [10; 11]. However, while conservative exercise therapy is strongly encouraged for those individuals diagnosed with KOA, low-load resistance training (LLRT) is often the only feasible method of treatment as this does not exacerbate joint pain and inflammation. However, high-load strength training (HLRT) effectively enables both strength and hypertrophic muscle adaptations [12]. Therefore, the American College of Sports Medicine (ASCM) guidelines recommend training intensities of at least 70% of 1 Repetition Maximum (RM) when wanting to induce strength increments [13]. Unfortunately, these levels of exercise intensity also imply substantial loading of the degenerated intra- and peri-articular structures, making its implementation in OA-associated exercise therapy often not feasible [14]. However, due to its significant correlation with function, lower limb strength training, specifically targeting the Quadriceps, remains crucial in the rehabilitation of KOA [15]. By improving both muscle mass and strength of the Quadriceps, the stability of the knee joint increases while also improving shock-absorbing capabilities [16]. Recently, the use of blood flow restriction training (BFRT) combined with low-load resistance training has emerged as a possible substitute for high-load strength training. With BFRT, a cuff is applied around the proximal aspect of the affected limb, causing partial arterial and full venous occlusion, thereby inducing localized hypoxia and the accumulation of metabolites, mimicking the effects of high load resistance training, albeit without heavy loads [17]. Consequently, BFRT might offer a suitable and more effective alternative for KOA patients who are not (yet) eligible for TKA compared to traditional exercise therapy.