Kinesiological / Dietary Supplement Intervention in Knee Osteoarthritis

The goal of this clinical trial is to assess the effectiveness of dietary supplement combined with exercise in managing knee osteoarthritis (KOA). The main questions it aims to answer are:

* Is adding a dietary supplement to exercise additionally effective in managing KOA?
* Is adding exercise to the dietary supplement additionally effective in managing KOA?

Participants will be given in three groups:

1. Real dietary supplement alone
2. Real dietary supplement with exercise
3. Placebo dietary supplement with exercise

Investigators will compare groups 1 and 2, or 2 and 3, to answer the research questions.

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.

Participant recruitment will take place at the Community Healthcare Center dr. Adolf Drolc Maribor based on the doctor's recommendation. Following an informed discussion about the study and potential risks, all patients providing written consent will undergo a one-week screening period to determine eligibility for study entry. Upon reaching week 0, patients meeting the eligibility criteria will be randomly assigned in a 1:1:1 ratio to receive either dietary supplements alone, dietary supplements combined with exercise, or placebo dietary supplement combined with exercise.

The effects of the kinesiological / dietary supplement intervention on selected measures will be assessed using a test battery, before and after the 12 week intervention, and at a 6-week follow-up.

Exercise / test batery will be conducted at Community Healthcare Center dr. Adolf Drolc under the supervision of an experienced kinesiologist / investigator.

Based on the posed research questions and hypotheses, investigators would like to highlight the following planned statistical analyses. In the case of bilateral KOA, investigators will analyze the more affected knee for differences between groups. In addition to descriptive statistics, investigators will assess normal distribution and homogeneity of variances. Differences between groups will be tested using two-way repeated measures analysis of variance (factor 1 = group, factor 2 = time) and paired two-tailed post-hoc t-tests with Bonferroni correction. The main comparison will be addressed with a 2x2 two-way analysis of variance. The first research question will be addressed with a 2x2 two-way analysis of variance, including groups 2 and 3. The second research question will be addressed with a two-way analysis of variance, including groups 1 and 2. Additionally, effect size will be calculated. The level of statistical significance will be set at p\<0.05.

Eligibility Criteria:
Inclusion Criteria:

* knee osteoarthritis of one or both knee
* severity of knee osteoarthritis based on Kellgren-Lawrence radiographic grade 1-3
* knee pain between 4 and 7 (using a 0-10 scale)

Exclusion Criteria:

* Age \<55 years
* Kellgren \& Lawrence grade 4 of knee osteoarthritis
* Acute knee injuries within the last 6 months
* Knee pain not associated with knee osteoarthritis
* History of knee or hip endoprosthesis
* Surgery on the back, hip, knee, ankle, or foot within the last 12 months
* Health issues or musculoskeletal limitations affecting strength training and mobility more than knee pain (e.g., lower back pain, hip pain)
* Rheumatoid arthritis, gout
* Neurological conditions (Alzheimer's disease, Parkinson's disease, metabolic diseases affecting the nervous system)
* Muscular or joint diseases/injuries affecting lower limb function (e.g., hip and/or ankle osteoarthritis, sprains, fractures)
* Internal medical conditions (cardiovascular, pulmonary, oncological, diabetes with late complications - diabetic foot, neuropathies) affecting physical performance
* Stroke or similar condition with consequences on motor skills and/or cognition (inability to provide consent)
* Balance disorders, known vestibular system impairment
* Body Mass Index \> 32
* Structured strength training exceeding 30 minutes per week
* Corticosteroids and/or hyaluronic acid (intra-articular) use in the last 6 months
* Individuals taking joint health dietary supplements, like glucosamine, chondroitin, or collagen, will need to halt use for at least 30 days before measurements to avoid affecting study outcomes