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Updated: Jun 2, 2026
Software-Assisted Quantitative Measurement of Osteoarthritic Subchondral Bone Thickness
Published on: March 18, 2022
Comparison of MRI-based assessment systems for osteoarthritic knees: the irregularity index system and WORMS
Kei O Matsuki1, Takahisa Sasho, Koichi Nakagawa
1Department of Orthopaedic Surgery, Graduate School of Medicine, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba, 260-8670, Japan.
Purpose:
Several MRI-based evaluation systems for osteoarthritis (OA) of the knee have been developed. Among them the whole-organ magnetic resonance imaging score (WORMS), which evaluates the status of the entire knee joint, appears to be representative. We developed an irregularity index system to measure irregularities of the contours of the femoral condyle on MRI. Only the contour of the condyle was assessed by the irregularity index, whereas several items comprising the knee joint were taken into account by WORMS. This study compared the irregularity index and WORMS in terms of their correlations with clinical scores.
Methods:
Thirty-one medial-type OA knees were studied. Kellgren-Lawrence grading was used for X-ray grading: 8 were grade II, 11 were grade III, and 12 were grade IV. Japanese Orthopaedic Association scores and Japanese knee osteoarthritis measure scores were used for clinical assessments. We determined the correlations between MRI-based assessment scores and clinical scores.
Results:
Both the irregularity index and WORMS exhibited positive correlations with these clinical scores. The irregularity index was associated with bone cysts of the medial compartment and menisci in the articular features of WORMS.
Conclusions:
These MRI-based methods are useful for evaluating OA severity. However, the irregularity index may have advantages over WORMS because of its semi-automatic features.
Insights
The irregularity index, an MRI method for knee osteoarthritis (OA), correlates with clinical scores and may offer advantages over the Whole Organ Magnetic Resonance Imaging Score (WORMS) due to its semi-automatic nature.
Area of Science:
- Orthopedics
- Radiology
- Medical Imaging
Background:
- Osteoarthritis (OA) of the knee is a prevalent condition requiring accurate assessment.
- Magnetic Resonance Imaging (MRI) offers detailed joint evaluation for OA.
- Existing MRI scoring systems, like the Whole Organ Magnetic Resonance Imaging Score (WORMS), assess multiple knee structures.
Purpose of the Study:
- To compare a novel irregularity index for femoral condyle contour assessment with the established WORMS.
- To evaluate the correlation of both MRI-based methods with clinical OA severity scores.
- To determine the potential advantages of the irregularity index in OA evaluation.
Main Methods:
- The study included 31 knees with medial compartment OA, graded using Kellgren-Lawrence scale (grades II-IV).
- Clinical assessment utilized Japanese Orthopaedic Association (JOA) and Japanese Knee Osteoarthritis Measure (JKOM) scores.
- Correlations between the irregularity index, WORMS, and clinical scores were analyzed.
Main Results:
- Both the irregularity index and WORMS demonstrated positive correlations with clinical OA severity scores.
- The irregularity index showed associations with specific features like bone cysts and meniscal status within the WORMS framework.
- These findings suggest both MRI methods are valuable for assessing OA.
Conclusions:
- MRI-based assessments, including the irregularity index and WORMS, are effective for evaluating knee OA severity.
- The irregularity index may offer practical advantages over WORMS due to its semi-automatic quantification.
- Further research could explore the clinical utility and broader application of the irregularity index in OA management.
