Development of a novel micro-CT based scoring system for the assessment of joint structure in a rat model of inflammatory knee osteoarthritis

Q: Why is a new micro-CT scoring system needed for knee osteoarthritis research?

Traditional histology requires animal sacrifice, is time-consuming, and evaluates limited sections, making whole-joint assessment difficult. Micro-CT enables non-invasive 3D visualization but previously lacked detailed cartilage-focused assessment, motivating the new scoring system.

Q: How was osteoarthritis induced and scored in the rat model?

Right knees of 24 Wistar male rats were injected with varying MIA concentrations (0.2, 0.5, 1, 3 mg). After 28 days, joints were scanned by micro-CT, segmented into 10 compartments, and each compartment was scored (0–4) to compute a total joint score.

Sep 29, 2026

Uploaded by Quinn Holloway

Osteoarthritis (OA) is a degenerative joint disease accompanied by inflammation, and conventional histological assessment is constrained by the need for animal sacrifice, limited tissue sections, and sampling bias. A novel micro-computed tomography (micro-CT)-based three-dimensional scoring system was developed to quantify joint structure changes in a rat model of monoiodoacetate (MIA)-induced inflammatory knee OA. The system showed excellent interobserver reliability and strong correlation with a modified Mankin histological score.

LanguageEnglish

CategoryHealthcare

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Pages8

Reading Time20 min

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Introduction

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Original Article | Basic and Mechanism Sciences Development of a novel micro-CT based scoring system for the assessment of joint structure in a rat model of inflammatory knee osteoarthritis Takuya Takata1, Tatsunori Ikemoto1, Young-Chang Arai2, Yusuke Ohmichi3, Mika Ohmichi3, Kohei Hashimoto1, Masaki Nakano1, Nobunori Takahashi1^ 1Department of Orthopedics, School of Medicine, Aichi Medical University, Nagakute, Japan; 2Department of Pain Medicine, Aichi Medical University, Nagakute, Japan; 3Department of Anatomy II, Kanazawa Medical University, Kahoku, Ishikawa, Japan Contributions: (I) Conception and design: T Takata, T Ikemoto, YC Arai; (II) Administrative support: Y Ohmichi, M Ohmichi, M Nakano, N Takahashi; (III) Provision of study materials or patients: T Ikemoto, YC Arai, Y Ohmichi, M Ohmichi; (IV) Collection and assembly of data: T Takata, T Ikemoto, YC Arai, K Hashimoto; (V) Data analysis and interpretation: T Takata, T Ikemoto, Y Ohmichi, M Ohmichi, K Hashimoto, M Nakano, N Takahashi; (VI) Manuscript writing: All authors; (VII) Final approval of manuscript: All authors. Correspondence to: Tatsunori Ikemoto, MD, PhD. Department of Orthopedics, School of Medicine, Aichi Medical University, 1-1 Yazako Karimata, Nagakute, Aichi, 480-1195, Japan. Email: [tatsunon31@gmail.com](tatsunon31@gmail.com). Background: Osteoarthritis (OA) is a degenerative joint disease involving cartilage loss and inflammation. Traditional histological evaluation is limited. Micro-computed tomography (micro-CT) offers non-invasive three-dimensional (3D) joint visualization but lacks detailed cartilage assessment. This study developed and evaluated a novel micro-CT-based scoring system for joint structure in a rat model of mono-iodoacetate (MIA)-induced OA. Methods: OA was induced in the right knees of 24 Wistar male rats using varying MIA concentrations (0.2, 0.5, 1, 3 mg). After 28 days, knee joints were scanned using micro-CT and segmented into 10 compartments. Degenerative changes in each compartment were scored (0–4), and a total joint score was calculated. Histological evaluation using a modified Mankin score was performed on sagittal sections of the patellar groove. Interobserver reliability and correlations between micro-CT joint scores and Mankin scores were analyzed statistically. Results: The micro-CT 3D imaging scoring system demonstrated excellent interobserver reliability [interclass correlation coefficient (ICC) >0.75 for most compartments] . Micro-CT joint scores revealed statistically significant differences in joint degeneration between the highest MIA dose group (3 mg) and the lower dose groups (0.2 and 0.5 mg) . Notably, micro-CT could differentiate between the 0.2 mg and 1mg groups, which was not fully reflected in histological scores. A strong correlation was found between the total micro-CT joint score and the modified Mankin score (ρ=0.8, P<0.001) . Conclusions: The novel micro-CT-based 3D imaging scoring system provides a reliable method for quantifying gross degenerative changes in rat knee joints in the MIA-induced OA model. While it does not directly assess cartilage, its correlation with histological findings suggests its utility as a complementary tool for evaluating overall joint degeneration. Keywords: Micro-computed tomography (micro-CT); knee osteoarthritis (knee OA); rat model; joint structure; scoring system Submitted Jul 07, 2025. Accepted for publication Nov 04, 2025. Published online Dec 24, 2025. doi: 10.21037/atm-25-101 View this article at: [https://dx.doi.org/10.21037/atm-25-101](https://dx.doi.org/10.21037/atm-25-101) ^ ORCID: 0000-0002-4521-7639. © AME Publishing Company. Ann Transl Med 2025;13(6):73 | [https://dx.doi.org/10.21037/atm-25-101](https://dx.doi.org/10.21037/atm-25-101) Page 2 of 8 Takata et al. Micro-CT evaluation for rat knee OA Introduction Osteoarthritis (OA) is a chronic degenerative disease characterized by the degeneration and loss

FAQs

Why is a new micro-CT scoring system needed for knee osteoarthritis research?

Traditional histology requires animal sacrifice, is time-consuming, and evaluates limited sections, making whole-joint assessment difficult. Micro-CT enables non-invasive 3D visualization but previously lacked detailed cartilage-focused assessment, motivating the new scoring system.

How was osteoarthritis induced and scored in the rat model?

Right knees of 24 Wistar male rats were injected with varying MIA concentrations (0.2, 0.5, 1, 3 mg). After 28 days, joints were scanned by micro-CT, segmented into 10 compartments, and each compartment was scored (0–4) to compute a total joint score.

What evidence supports reliability and validity of the micro-CT scoring system?

The micro-CT 3D imaging scoring system demonstrated excellent interobserver reliability with interclass correlation coefficients above 0.75 for most compartments. Total micro-CT joint scores showed a strong correlation with the modified Mankin histological score (ρ=0.8, P<0.001).

Sep 29, 2026

Uploaded by Quinn Holloway