Skeletal muscle weakness and muscle fatigue are commenly presented in patients with a rheumatic muscoloskeletal diseaese (i.e. RMD-induced muscle weakness) such as rheumatoid arthritis (RA), osteo-arthritis (OA), spondylarthritis (SpA) and gout. Muscle force can be reduced by 25 till 75% and it persists even though patients are treated with effective novel anti-inflammatory drugs that target the primary inflammation. This compromises the quality of life of patients with an RMD and causes a high socio-economic burden.  Currently there is insufficient knowledge about the disease pathophysiology and treatment opportunities are limited. It is for these reasons that we are focusing on unraveling the pathophysiology of RMD-induced muscle weakness and try to find novel diagnostic and therapeutic tools that can help to understand and target this clinical problem.