For the App group, we installed the app from the store in their smart phone or tablets, made their account using the same email they use in their smart phone store. the participant was informed if they cannot follow the animated image in the app, they can re-launch the program and start to follow.

For the paper group, the participants were provided with a hard copy of the exercise program; we gave one paper of all nine exercises.

Simple progressive strengthening exercise program for lower-extremity muscles (knee extensor and hip abductor muscles), the program has been evident to be significantly effective in improving self-reported knee pain and function. This program included: 1) Isometric quadriceps contraction, 2) Isotonic quadriceps contraction, 3) Isotonic hamstring contraction, 4) Isotonic quadriceps contraction with resistance band, 5), straight leg raising, 6) Side-lying hip abduction, 7) Partial Squats,

Adherence rate obtained as a percentage of the exercise done out of the total number of prescribed exercises. The self-reported adherence is a self-report, all the participants received an exercise log and asked to check on the date of the completed exercise. To calculate adherence, the total number of done exercises for each participant was divided by 84 and 182, which were the total number of prescribed exercises for the 3rd and 6th week period respectively.

Pain intensity over the previous week evaluated with The Arabic Numeric Pain Rating Scale (ANPRS) which is a reliable and valid scale for assessing pain in knee osteoarthritis. It is a 0 to 10 numerical rating scale in which "0" indicates "no pain" and "10" indicates "worst pain".

Used to assess the physical function. It is reliable and valid measure for assessing the severity of knee OA in term of pain and physical function. The reduced ArWOMAC has two subscales and twelve elements in total, the pain subscale includes five elements and the physical function subscale includes seven elements. Likert-scale is applied where the response of each element comes with five levels showing varying intensity degrees that range from 0 to 4, where four is assigned for "extreme" and 0 assigned for "none". The analysis entails collecting and summing up the scores for elements in both subscales to get the total scores (for pain 0-20, for function the scores are 0-28

To evaluate lower-limb muscle strength, the five-times sit-to-stand test used. It is a part of the Short Physical Performance Battery instrument; it is simple, fast, inexpensive and reproducible. It is valid (115) and has excellent test-retest reliability for older adults in general and osteoarthritic older adults. The test utilized an armless chair; the seat rises 46 cm above the ground. The participant starts out by sitting on the chair with arms crossed over the chest. Awarding points is a function of the required time to complete the test. The contributor takes 4 points for the time, not exceeding 11.19 seconds; 3 points when the consumed time is greater than 11.20 and less than 13.69 seconds; two points when the required time ranges from 13.70 and 16.69 seconds; one point if the consumed time is greater than 16.7 seconds; 0 points if the participant cannot complete the test or need more than 60 seconds to finish it.