Hip Osteoarthritis is a very common and widespread disease of today. When all conservative methods for suppressing pain and reducing the symptoms of the disease are exhausted, by doctor's decision and if the patient as such is a suitable candidate, an operative procedure of implantation of artificial hip joint is suggested. Like any invasive procedure, the procedure also brings with it certain risks, but, with the progress of medicine, the success of such treatment is very high, and the frequency of complications is acceptable. The materials used must be resistant and after installation mustn’t react and release harmful substances. The surgical procedure differs depending on the direction from which the hip joint is accessed, and one of most commonly used is the anterolateral access. In addition to the operation itself appropriate rehabilitation is also required, and there is a number of physical, psychological and environmental factors that influence the success of treatment. The goal of rehabilitation is to restore the function of all surrounding structures and enable a quick return of daily life activities. The known researches carried out so far and work reviews indicate that the strength of the abductor muscles after hip endoprosthesis installation, is weaker compared to the strength before the procedure. Also, a large number of studies show a statistically significant influence of the body mass index on the strength of the abductor muscles after the surgery. This paper describes the research which included 68 subjects whose abductor muscle strength was tested before and after the operation. In addition to muscle strength, the body mass index was calculated. The results obtained cannot be identified with those known so far, that is, it has not been proven that the strength of the hip abductors after surgery is weaker than before and that the body mass index has a negative effect on recovery of mentioned muscles.