Correlation of WOMAC and KOOS scores to tibiofemoral cartilage loss on plain radiography and 3 Tesla MRI: data from the osteoarthritis initiative

Purpose

The purpose of this study was to determine the correlation between the Western Ontario and McMasters Universities Osteoarthritis Index (WOMAC) and Knee Injury Osteoarthritis Outcomes scores (KOOS) and the degree of tibiofemoral cartilage loss on plain radiography and 3T magnetic resonance imaging (MRI). We hypothesize that these subjective outcome scores will have a significant correlation to quantitative joint space loss.

Methods

Data used in the preparation of this article were obtained from the osteoarthritis initiative (OAI) database (OAI public use data sets kMRI_QCart_Eckstein18 and kXR_QJSW_Duryea16). Four hundred and forty-five patients had WOMAC/KOOS scores, quantitative tibiofemoral joints space width on plain radiographs and quantitative tibiofemoral cartilage thickness and per cent full thickness cartilage loss on 3T MRI. Joint space width on plain radiographs was correlated to cartilage thickness on MRI, and WOMAC/KOOS scores were correlated to the degree of cartilage loss using Pearson correlation coefficients.

Results

There was a statistically significant correlation between medial and lateral compartment cartilage thickness on MRI and medial and lateral joint space width on plain radiography (r = 0.86, r = 0.80) (p < 0.001). KOOS knee pain score was significantly correlated to increasing per cent full thickness cartilage loss in the medial femoral compartment (r = 0.34) (p < 0.001). KOOS symptom score was significantly correlated to decreasing joint space width in the medial (r = 0.16) and lateral (r = 0.15) compartment and increasing per cent full thickness cartilage loss in the medial femoral compartment (r = 0.36) (p < 0.001). No WOMAC score was correlated to degree of joint space width, cartilage thickness or per cent full thickness cartilage loss (n.s).

Conclusion

The WOMAC and KOOS scores are poor indicators of tibiofemoral cartilage loss, with only the KOOS symptom and knee pain score being weakly correlated. Osteoarthritis is a multifactorial process and the need to treat patients based off their symptoms and rely on radiographs as confirmatory modalities, and not diagnostic modalities, when talking about OA and medical intervention.

Level of evidence

Level 2.