Dose-response relationship of in vivo ambulatory load and mechanosensitive cartilage biomarkers-The role of age, tissue health and inflammation: A study protocol

Abstract

Objective: To describe a study protocol for investigating the in vivo dose-response relationship between ambulatory load magnitude and mechanosensitive blood markers of articular cartilage, the influence of age, cartilage tissue health and presence of inflammation on this relationship, and its ability to predict changes in articular cartilage quality and morphology within 2 years.

Design: Prospective experimental multimodal (clinical, biomechanical, biological) data collection under walking stress and three different load conditions varied in a randomized crossover design.

Experimental protocol: At baseline, equal numbers of healthy and anterior cruciate ligament injured participants aged 20-30 or 40-60 years will be assessed clinically and complete questionnaires regarding their knee health. Biomechanical parameters (joint kinetics, joint kinematics, and surface electromyography) will be recorded while performing different tasks including overground and treadmill walking, single leg balance and hopping tasks. Magnetic resonance images (MRI) of both of knees will be obtained. On separate stress test days, participants will perform a 30-minute walking stress with either reduced (80% body weight (BW)), normal (100%BW) or increased (120%BW) load. Serum blood samples will be taken immediately before, immediately after, 30, 120 and 210 minutes after the walking stress. Concentration of articular cartilage blood biomarkers will be assessed using enzyme linked immunosorbent assays. At 24-month follow-up, participants will be again assessed clinically, undergo an MRI, complete questionnaires, and have a blood sample taken.

Conclusion: The study design provides a standardized set up that allows to better understand the influence of ambulatory load on articular cartilage biomarkers and thereby extend current knowledge on in vivo cartilage metabolism and mechanosensitivity. Further, this study will help to elucidate the prognostic value of the load-induced cartilage biomarker response for early articular cartilage degeneration.

Trial registration: The protocol was approved by the regional ethics committee and has been registered at clinicaltrials.gov (NCT04128566).

Fig 1. Schedule of enrollment and assessments.

Fig 2. Planned participant characteristics.

Injury subcategories healthy and ACL injured and the age subcategories 20 to 30 and 40 to 60 years. ACL–Anterior cruciate ligament.

Fig 3. Illustration of the study design.

Overview and timeline of the measurements of baseline, 12-month follow-up and 24-month follow-up data collection. KSS–Knee Society Score; KOOS–Knee Injury and Osteoarthritis Outcome Score; MRI–magnetic resonance imaging; FS-PD TSE–fat saturated proton density turbo spin echo; qDESS–quantitative double-echo steady-state.

Fig 4. Marker and electromyography electrodes placement during the biomechanical assessment.

Surface electromyography electrodes (blue circles; electrodes on gluteus medius under the pants) and marker placement (bright dots) for 3D motion analysis in front (left), back (middle) and side (right) view.

Fig 5. The applied loading conditions during walking stress.

Reduced load (80% bodyweight (BW)) is achieved using a harness connected to a pneumatic pulley system (left). During normal load (100%BW) the BW is not altered (middle). Increased load (120%BW) is achieved using a weight vest (right).