[1] Kristiansund Hosp, Dept Orthoped Surg, N-6518 Kristiansand, Norway
[2] Univ Oslo, Inst Clin Med, Fac Med, Oslo, Norway
[3] Akershus Univ Hosp, Dept Orthoped Surg, N-1478 Lorenskog, Norway
[4] Univ Oslo, Inst Clin Med, Campus Ahus, N-1478 Lorenskog, Norway
[5] Akershus Univ Hosp, Dept Hlth Serv Res, N-1478 Lorenskog, Norway
[6] Norwegian Sch Sports Sci, Oslo Sports Trauma Res Ctr OSTRC, Postboks 4014 Ulleval Stad, N-0806 Oslo, Norway
[7] Norwegian Univ Sci & Technol, Inst Neuromed, Fac Med, N-7491 Trondheim, Norway