Patellar osteochondral involvement in chondromalacia patella: An exploratory routine MRI-based three-tier framework

Area of Science:

• Radiology
• Orthopedics
• Medical Imaging

Background:

• Patellar cartilage and subchondral bone damage often occur together.
• Assessing combined involvement is crucial for understanding knee osteoarthritis progression.
• Standard MRI grading systems may not fully capture the complexity of patellofemoral osteochondral disease.

Purpose of the Study:

• To evaluate if routine knee MRI can reveal reproducible patterns of combined patellar cartilage and subchondral bone involvement.
• To introduce and test an exploratory three-tier MRI framework focused on patellar osteochondral structures.
• To assess the reliability and correlation of cartilage and bone damage grading.

Main Methods:

• Retrospective analysis of 200 knee MRI examinations.
• Grading of patellar cartilage damage (Amax 0-4) and subchondral bone abnormalities (Bmax 0-3).
• Categorization into Tier 1 (low-burden), Tier 2 (discordant), and Tier 3 (concordant advanced) involvement.
• Subgroup analysis comparing 1.5-T and 3-T MRI field strengths.

Main Results:

• High interobserver agreement for Amax (κ=0.82) and Bmax (κ=0.85), excellent for composite score (ICC=0.91).
• Positive correlation between cartilage and bone damage grades (rho=0.637, p<0.001).
• Tier 1, 2, and 3 patterns observed in 43.5%, 23.5%, and 33.0% of cases, respectively.
• No significant difference in framework categories between 1.5-T and 3-T, though Amax grade distribution differed (p=0.021).

Conclusions:

• Routine knee MRI can identify reproducible patterns of patellar osteochondral involvement.
• The proposed framework describes low-burden, discordant, and concordant advanced patterns.
• This exploratory framework aids in characterizing combined cartilage-bone disease but is not a validated staging system.