Background: Mucopolysaccharidosis (MPSs) are a group of metabolic disorders caused by several different enzyme deficiencies that cause multi-systemic affection. Aim:The aim of this study was to assess the capability of ultrasound elastography (SE) in evaluating the tendons stiffness in patients with diagnosis of MPSs correlating with clinical and physical examination. Method:We evaluated 15 patients affected of MPS during a year and a half (6 men and 9 women, median age of 10 years, range 3-39). General data such as the type of mucopolysaccharidosis, the enzymatic deficiency, storage product, genetic defect, treatments and general symptoms were recorded. Exhaustive orthopedic examination has been performed and orthopedic surgeries have been recorded. The functional exercise capacities were evaluated with the Six-Minute Walk Test. For Sanfilippo disease we used a disability scale that measures ambulation, behavior, speech, swallowing, and epilepsy with a score in each category. One paediatric radiologist with specific training in musculoskeletal disorders performed the ultrasound elastography examinations in all subjects. Results:We have found echographic alterations in different locations of patients with mucopolysaccharidosis that correspond to what is found in the elastography. Conclusion:The results of this work are promising as to the usefulness of elastography in the assessment of tissue stiffness in deposit diseases such as MPSs. Their greater sensitivity to detect deposits may be useful for us to evaluate the enzymatic treatments, the BMT or the surgical treatments that we perform to these patients. Level III of evidence