The hypothesis is that participants who receive the dietary supplement along with exercise will experience greater reduction in pain level, improved physical function, and enhanced quality of life compared to those who receive a placebo combined with exercise or dietary supplement alone. conditions: Osteoarthritis, Knee studyType: INTERVENTIONAL phases: NA allocation: RANDOMIZED interventionModel: FACTORIAL interventionModelDescription: The differences between groups will be tested using a two-way analysis of variance for repeated measures (factor 1 = group, factor 2 = time) primaryPurpose: SUPPORTIVE_CARE masking: TRIPLE maskingDescription: Placebo blinding / masked for dietary supplement whoMasked: PARTICIPANT whoMasked: CARE_PROVIDER whoMasked: INVESTIGATOR count: 120 type: ESTIMATED name: Non-training Real Dietary Supplement (G1) name: Training Placebo Dietary Supplement (G2) name: Training Real Dietary Supplement (G3) measure: Change from baseline in severity grading of knee osteoarthritis from X-ray Images at week 12 measure: Change from baseline in thickness of the articular cartilage and cross-section of muscles around knee joint at week 12 measure: Change from baseline in self-assessment pain, stiffness, and physical function (WOMAC questionaire) at week 12 measure: Change from baseline in self-assessment quality of life (SF-36 questionaire) at week 12 measure: Change from baseline in time spent sleeping, awake/sedentary, and physical activity within 24 hour (DAB-Q) at week 12 measure: Change from baseline in knee pain on visual analogue scale at week 12 measure: Change from baseline in static balance time at week 12 measure: Change from baseline in direction-specific amplitude from the center of pressure in static balance at week 12 measure: Change from baseline in direction-specific velocity from the center of pressure in static balance at week 12 measure: Change from baseline in direction-specific frequency from the center of pressure in static balance at week 12 measure: Change from baseline in number of repetitions in Chair Stand Test at week 12 measure: Change from baseline in time for Five Times Sit to Stand Test at week 12 measure: Change from baseline in number of repetitions in Arm Curl Test at week 12 measure: Change from baseline in lower body flexibility at week 12 measure: Change from baseline in upper body flexibility at week 12 measure: Change from baseline in 6-minute walk distance at week 12 measure: Change from baseline in maximal isometric voluntary contraction of knee flexor and extensor at week 12 measure: Change from baseline in explosive strength of knee extensor at week 12 measure: Change from baseline in 24-hour time use at week 12 measure: Change from baseline in presence of inflammatory markers in blood sample at week 12 sex: ALL minimumAge: 55 Years stdAges: ADULT stdAges: OLDER_ADULT facility: University of Primorska, Faculty of Health Sciences city: Izola zip: 6310 country: Slovenia name: Nejc Šarabon, PhD role: CONTACT phone: 05 662 64 66 phoneExt: +386 email: nejc.sarabon@fvz.upr.si name: Tina Čeh, MSc role: SUB_INVESTIGATOR lat: 45.53694 lon: 13.66194 facility: Community Healthcare Center dr. Adolf Drolc city: Maribor zip: 2000 country: Slovenia name: Jernej Završnik, PhD role: CONTACT phone: 02 2286 257 phoneExt: +386 email: jernej.zavrsnik@zd-mb.si name: Tina Čeh, MSc role: SUB_INVESTIGATOR lat: 46.55472 lon: 15.64667 hasResults: False