2 Weekly Intra-articular Hyaluronan Knee Injections, Given 1 wk. Apart, of HYMOVIS Combined With Physical Exercise Program (PEP) Compared to PEP Alone, in Relatively Young, Active Population of Subjects With Patellofemoral Osteoarthritis (PFOA) and/or Tibiofemoral Osteoarthritis (TFOA)