All exercises were repeated each for 3 sets with a break of 1-2 minutes between the sets. The two static exercises consisted of 6 repetitions of 6 seconds hold in each position with 6 seconds rest between each contraction. The dynamic exercise was performed with 6 repetitions through the whole range of motion with 2-3 seconds for each repetition without any rest between the repetitions. A break between the repetitions was added if necessary to avoid pain (Table 1). Patients repeated the exercise session one time per week under supervision of a physiotherapist, during 6 weeks. In addition, patients performed the exercise session twice per day seven days per week at home. Each exercise session lasted about 20 - 25 minutes.