Patellofemoral Cartilage Degradation Based on T1ρ Relaxation Times Varies Inversely With BMI After Patellar...

Area of Science:

• Orthopedics and Sports Medicine
• Biomedical Imaging
• Rheumatology

Background:

• Elevated body mass index (BMI) is a known risk factor for knee osteoarthritis.
• Limited data exist on the relationship between BMI and knee cartilage properties immediately following traumatic injury.

Purpose of the Study:

• To investigate the correlation between BMI and patellofemoral cartilage properties using T1ρ relaxation times after patellar dislocation.
• To test the hypothesis that high BMI is associated with cartilage degradation (indicated by long T1ρ relaxation times) in both healthy and post-dislocation knees.

Main Methods:

• A cross-sectional study involving 61 patients (underweight to obese, BMI < 40 kg/m²).
• Magnetic resonance imaging (MRI)-based T1ρ relaxation time mapping was used to assess patellofemoral cartilage.
• Patients included those with first-time patellar dislocation, multiple dislocations, and healthy controls. Mean T1ρ relaxation times were correlated with BMI.

Main Results:

• In healthy controls, higher BMI correlated with longer T1ρ relaxation times, indicating cartilage degradation, across most patellofemoral regions.
• Conversely, in patients with first-time or multiple patellar dislocations, lower BMI correlated with longer T1ρ relaxation times in several patellofemoral and trochlear groove regions.
• The findings were statistically significant (P < .05) with R² values ranging from 0.24 to 0.63.

Conclusions:

• High BMI is associated with cartilage degradation in healthy knees, but unexpectedly, low BMI is linked to cartilage degradation after patellar dislocation.
• Overweight and obese individuals may not have an immediate heightened risk of progressive cartilage degradation post-dislocation.
• Underweight and healthy-weight individuals experiencing traumatic patellar dislocation may face early cartilage degradation, potentially initiating posttraumatic osteoarthritis.