**5.5 Life with total hip arthroplasty**

Charnley believed that THA is appropriate for older people with limited physical expectations (Charnley and Feagin 1973). Later on, younger and more active patients were indicated for prosthetic hip surgery and the expectations of these patients have increased continually. In fact, younger patients who are treated by THA wish to return to recreational and even competitive sports activity. At the same time, patient activity is considered one of the most important factors in the risk of failure especially via increased wear-rate of bearing surfaces (Schmalzried et al. 2000). By this way, *those who experience high-levels of activity are at increased risk for failure due to aseptic loosening and osteolysis*, and vice versa, lower impact activities are less likely to create conditions appropriate to loosening (Kilgus et al. 1991; Lubbeke et al. 2011). Regarding the stability of bone-implant interface, there may be a concern about cracks followed by fracture of the cement mantle in association with highimpact load. Surgeons should advise patients with THA that all high-impact activities could compromise the durability of their implant, especially in terms of accelerated wear and premature aseptic loosening. Another possible concern is risk of fall and direct contact during these sport activities that could lead to catastrophic failure, periprosthetic fracture or dislocation of THA. In addition, patients should know that return to a high-load level is not possible without achieving a very good muscle condition and also appropriate skills in their coordination beforehand as muscles can share the forces traversing an artificial joint and thus could prevent its damage. On the other hand, regular repetitive physical activities positively affect both the bone (in accordance with Wolff´s law) and muscles near the artificial joint (Clifford and Mallon 2005; Wilson and Villar 2011).
