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[Magnetic Resonance Imaging, Arthroscopy and Near-Infrared Spectroscopy (NIRS) for Grading Osteoarthritis in the Knee].

PURPOSE
This study was aimed to evaluate the meaningfulness of the MRI Score WORMS (Whole Organ Magnetic Resonance Imaging), the arthroscopic WOAKS (Whole Organ Arthroscopic Knee Score) and the result of NIRS (near-infrared spectroscopy) measurements.


MATERIALS AND METHODS
A total of 49 patients with knee pain (> 3 months) underwent MRI with a standardised protocol. In the results the WORMS was calculated. The WOAKS was calculated from the results of an arthroscopic evaluation. In the same procedure, NIRS measurements were performed in the identical 14 regions of interest. From these measurements, the WOAKS_NIRS was calculated.


RESULTS
The highest grade of degeneration in all evaluations was found in the patella. The medial compartment showed moderate lesions compared with the lateral compartment. The relative WORMS was only 3.7 % (95 % CI 2.8-4.6; 0-15.6 %). During arthroscopy, we calculated a mean WOAKS of 15.2 % (95 % CI 13.2-17.2; 5-39 %). The degree of joint degeneration was highest in NIRS measurements. The mean WOAKS_NIRS was 50.9 % (95 % CI 48.1-53.7 %). These differences are significant (p < 0.001).


CONCLUSION
The methods to detect early cartilage degenerations in MRI are flawed. Thus in our patients, we detected a full grade of degeneration in only 3.7 % of the patients. Arthroscopy mostly gives higher damage within the knee joint. The initial stages of cartilage lesion are usually undetectable. Spectroscopy has the best sensitivity for the evaluation of early degeneration within the hyaline cartilage. The clinical relevance of our results is still unclear. Further outcome studies are needed.