Osteoarthritis (OA) is a degenerative disease of the movable joints affecting the elderly population worldwide. It is characterized by localized loss of cartilage, remodelling of adjacent bone, and bony overgrowth because of a maladaptive cartilage repair process. Its presentation is highly variable between individuals, with some common features, such as joint pain, impaired movement, tenderness, crepitus, occasional effusion, and local inflammation^1,2.

Besides hand and hip, the knees are frequently affected by OA whereas the prevalence is higher in women. Knee pain is a common complaint and prevalence increases with age³. Osteoarthritic knees show degeneration of the cartilage and pathological changes of the bone. Knee OA typically develops gradually over a period of years and is also termed degenerative osteoarthritis. Classical symptoms are pain, stiffness, limited range of motion and localized swelling. As knee osteoarthritis progresses, symptoms generally become more severe. The diagnosis of OA can usually be made on the basis of the initial history and examination. According to the American College of Rheumatology (ACR) radiographic and clinical knee OA diagnosis criteria include pain plus, at least, three of the following aspects: age over 50, morning stiffness (< 30 min), crepitus and presence of osteophytes. X-rays are typically used to confirm the diagnosis of osteoarthritis and can reveal osteophytes at the joint margins, joint space narrowing and subchondral bone sclerosis. The most common system to grade radiographic severity is the Kellgren and Lawrence grading system².

There is no known cure for osteoarthritis, but treatments can help to reduce pain and maintain joint movement. Current recommendations for the management of OA include non-pharmacological interventions such as weight loss or exercise and pharmacological treatments with analgesics and anti-inflammatory drugs.

It is now increasingly recognized that, beyond meeting basic nutritional needs, nutrition may play a beneficial role in some diseases. Because the mechanisms of cartilage degradation in OA are multifactorial and some nutritional compounds usually contain multiple active compounds that target multiple pathways, nutrition could provide beneficial effects in the management of OA. Nutritional interventions are positioned to provide long-term rather than short-term effects. Although not a traditional inflammatory disease, symptoms of local inflammation and synovitis are present in many patients of OA. On this background, antioxidative and immune-modulating ingredients are recognized to be beneficial for OA. Several dietary supplements like glucosamine, chondroitin and collagen hydrolysate^4,5 have demonstrated benefits compared to placebo and active controls. Even so the effectiveness of these compounds is under discussion as they are cartilage structure compounds providing reported synergistic effects^6,7,8,9. Additionally, a recent meta-analysis describes small-to-moderate effects of collagen derivatives on pain alleviation (standardized mean difference [SMD] − 0.35, 95% confidence interval [CI] − 0.48 to − 0.22, moderate certainty) and function improvement (SMD − 0.31, 95%CI − 0.41 to − 0.22, high certainty) compared with the control in OA patients¹⁰.

In the tested formulation, the cartilage structure compounds are combined with vitamins and minerals to support the joint health synergistically. The aim of the pilot study was a proof of concept of the combination of substances to investigate the impact of the formulation on symptoms of OA patients with slight to moderate knee pain. To support symptom relief can greatly improve the quality of life and the mobility of the subject’s knees.

Subject characteristics and ethics

On average, subjects in the Verum group were 62.7 years old (95% CI: 60.3–65.1) and in the Placebo group 59.4 years old (95% CI: 55.3–63.6). There were no differences in age between groups (p = 0.1417). Overall, 28 women (53.8%) and 24 men (46.2%) participated in the study. This was similarly distributed in both study groups. Participants in verum group had on average a slightly but significantly higher BMI of 26.40 kg/m² (95% CI: 25.23–27.58) in comparison to participants in the placebo group with BMI of 24.26 kg/m² (95% CI: 22.70–25.82). Most subjects (52.9%) in the verum group had OA grade III in accordance with Kellgren classification. Grade II was most present in the placebo group (44.4%). Overall, participants of the verum group were slightly older, the proportion of overweight subjects was higher (64.7% vs. 50%) and had a higher radiographic severity (KL-grade 3) (52.9% vs. 27.8%) than in the placebo group (Table 1). Nevertheless, no significant differences between verum and placebo group concerning the Kellgren scores could be observed (chi-square test: 4.045, df = 2, p ≈ 0.133).

Ethical approval and study design.

This study was conducted in accordance with the guidelines for Good Clinical Practice (GCP) set forth by the International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use (ICH), and in accordance with the Declaration of Helsinki regarding the treatment of human subjects in a study. The study was registered in the German Clinical Trials Register (DRKS00029563).

Ethical approval

The ethical approval was obtained from the Institutional Review Board (IRB) of Landesärztekammer Baden-Württemberg on 18.05.2022.

Conduct of the study

The study was performed as randomized, placebo-controlled, double-blind, pilot study over a period of 12 weeks to assess parameters of OA symptoms. Prior to any measurements and screening for eligibility, all subjects were informed in detail about the study procedure and signed informed consent. Medical history and chronic medication has been reported (STable 1 and STable 2).

In case all inclusion and none of the exclusion criteria were met, subjects were enrolled (STable 3). When subjects fulfilled all inclusion and none of the exclusion criteria, being eligible for the study they were allocated randomly (with allocation scheme of 2:1) to one of the two study groups (verum and placebo, respectively) according to the randomization list. The randomization scheme was created by using the software DatInf Randlist Version1.5 (DatInf GmbH Tübingen)¹¹.

Study products (Dr. Böhm Gelenks complex as verum or cellulose tablets as placebo) were taken over a period of 12 weeks twice a day. Dr. Böhm Gelenks complex is a multinutrient food supplement with Glucosaminhydrochlorid, Chondroitinsulfate, Collagen complex with Type II collagen, mucopolysaccharids, hyaluronic acid, methylsulfonylmethan (MSM), selenium, manganese, vitamin C, vitamin E, vitamin D (Table 2). Verum and placebo had the same shape, color, smell and taste.

Osteoarthritis symptoms were assessed with KOOS questionnaire at baseline, after 6 and 12 weeks of intervention. To assess physical function and judge symptoms under load, participants were asked to perform a recommended core set of performance-based tests at beginning and end of intervention. Time to complete the tests/or number of repetitions and pain under movement were assessed.

In the current study, 265 subjects received the study information and were pre-screened via phone, wherefrom 59 subjects were screened for eligibility. Thereof, 54 subjects were enrolled in the study, wherefrom 52 subjects completed the study in its entirety (Scr, visit 1-visit 3). The medical history and chronic medication is given in ATable 2 and ATable 3. 2 subjects dropped out during study conduct (see Fig. 1).

All clinical procedures were conducted by trained study personnel under the oversight of the study physician. OA diagnosis and Kellgren–Lawrence grading were confirmed at screening by a board-certified orthopaedist based on radiographic or MRI images. At each on-site visit (V2 and V3), participants first completed the KOOS questionnaire and a global assessment under the guidance of a trained study nurse, then immediately performed the 30-second chair stand, the 40 m fast-paced walk, and the stair climb tests in that order, with approximately 2 minutes’ rest between tests as per the study SOP. KOOS was always administered prior to any physical testing to avoid exercise-induced pain bias.

KOOS questionnaire

KOOS is an extension of the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and is designed to survey more active people with knee injury and/or knee osteoarthritis¹². The subscores pain, symptoms, stiffness, activity of daily life, sport and recreation, as well as quality of life were evaluated using a 5-point Likert scale from 0 (no problems) to 4 (extreme problems). The sum score was calculated as the sum of the items included. Scores were transformed to a 0–100 scale, with 0 (extreme knee problems) to 100 (no knee problems). In addition, in orientation to the WOMAC questionnaire, WOMAC subscores pain and stiffness were calculated from the KOOS questionnaire.

Performance-based measures of physical function

In accordance with recommendations of OARSI¹³, the following performance-based tests were performed to assess physical function in individuals diagnosed with knee OA: 30-second chair stand test (maximum number of chair stand repetitions possible in a 30 s period are counted), 40 m fast paced walk test (fast-paced walking test over 4 × 10 m) and the stair climb test (SCT) (time it takes to ascend and descend a flight of stairs with 9 steps). Additionally, at rest before all performance-based tests and immediately after the SCT test, the level of pain in the target knee after was assessed using a Numeric rating scale (NRS: 0 (no pain) to 10 (extreme pain)). If both knees were affected by OA, the knee with more complaints was defined as the target knee. Time taken to complete the tests was recorded to the nearest 100th of a second with a digital stopwatch. A higher score indicated lower physical function.

SF-36

The SF-36 questionnaire is a self-administered questionnaire containing 36 items which takes about 5 min to complete. It measures health on eight multi-item dimensions [Physical Functioning (PF), Role-Physical (RP), Bodily Pain (BP), General Health (GH), Vitality (VT), Social Functioning (SF), Role-Emotional (RE) and Mental Health (MH)], covering functional status and wellbeing, and overall evaluation of health. The scales were combined in a Physical Component Summary (PCS) and the Mental Component Summary (MCS).

Global assessment

At baseline, V1, V2 and V3 patients had to judge the OA in the target knee within the last 48 h and the pain in the target knee within the last 4 weeks. At the end of the study, subjects were asked to rate the efficacy of the study product; to judge the OA in the target knee within the last 48 h compared to the beginning of the product intake; whether they would recommend the product to acquaintances/friends/family or whether they would continue to take the product.

Obtaining of biological samples

At screening and visit 3, blood sample were taken to determine safety parameters and confirmation of the subjects’ state of health. Blood sampling was performed after at least 10 h overnight fast. To control for confounding factors, a standardized a standardized dinner was taken the days before. In addition, subjects are asked to keep their nutrition and exercise habits over the whole study period.

Blood routine parameters, such as liver enzymes (GPT, GOT, γ-GT, AP), fat status (total cholesterol, LDL- and HDL- cholesterol, triglycerides), creatinine, uric acid as parameters of kidney function, and differential haemogram were assessed. In addition, the biomarkers hsCRP and COMP (cartilage oligometric protein). All blood parameters were measured in an accredited laboratory. For vital signs and routine hematology and biochemistry, we observed a slight increase in mean eosinophil counts from baseline in the verum arm (+ 0.07 × 10^9/L versus + 0.02 × 10^9/L in placebo) and a modest rise in triglyceride levels (+ 0.15 mmol/L versus + 0.05 mmol/L). All other vital-sign and laboratory parameters remained within normal ranges. Causality for these laboratory findings was adjudicated by the study investigator using WHO criteria and deemed ‘unlikely’ related to the intervention.

Safety, adverse events and concomitant medication

During the study intervention, subjects documented any adverse events (AE; unfavourable and unintended sign including an abnormal laboratory finding, symptom or disease) and concomitant medication in a subject’s diary. At each visit, changes in physical conditions, concomitant therapy, severity and outcome of AE were asked for, evaluated and recorded by investigator. All AEs were inquired and documented in accordance to ICH/GCP Guidelines in the electronical case report form (eCRF).

Randomization and blinding

All subjects received a screening number at screening (S001, S002,…). When subjects fulfilled all inclusion and none of the exclusion criteria, being eligible for the study they were allocated randomly (with allocation scheme of 2:1) to one of the two study groups (verum and placebo, respectively) according to the randomization list by means of consecutive counting following the schedule of their inclusion visit. Subjects received subject numbers (P101, P102…). Assignment of subject to screening number/subject number was documented in subject identification list. The subject/screening numbers further identified the subjects and their treatments, documents, etc. Only the investigator and study coordinator were allowed to have access to this list.

Temporary interruption of IMP is instituted for reversible safety triggers (e.g., Grade ≥ 3 TEAEs or clinically significant lab abnormalities) and resumed once events return to ≤ Grade 1. Permanent withdrawal from the study occurs in cases of SAEs, persistent non-compliance, or participant request for discontinuation.

The randomization scheme was created by using the software DatInf Randlist Version1.5 (DatInf GmbH Tübingen). According to the randomisation list, the study products were labelled with the randomization number (subject number) and time point of hand out. The randomization list was kept at Sponsor site.

Only the investigator and study coordinator were allowed to have access to this list.

Statistics

An intention-to-treat (ITT) analysis was performed. Delta changes between end of intervention and baseline and considering baseline as covariate was evaluated using ANCOVA statistics. To confirm results, the Student t-test was applied. If data were not normally distributed, the Mann Whitney test was applied. Baseline sclerotisation characteristics and change-from-baseline (CfB) descriptive statistics (mean ± SD) were calculated for both placebo and verum groups. Baseline group comparisons were performed using independent t-tests, while between-group differences in CfB were evaluated by ANCOVA with baseline values as covariates. ANCOVA and two-tailed t-test analysis were performed in SPSS 22 and a significance level of 0.05 was used. Within figures results are depicted as box plots or as bar charts if data represent descriptive information. Significance levels with p < 0.001 are indicated with ***, p < 0.01 with ** and p < 0.05 with *. For Global assessment questionnaire Chi square analysis and Fischer´s exact tests were performed. All statistics compared the efficacy after 12 weeks of treatment with baseline characteristics. To test for linearity of efficacy over time, R² values have been calculated via Pearson´s regression model including baseline values and the effects after 6 and 12 weeks of treatment. Results are plotted to compare placebo and verum group.