Evaluation of the prevalence, lesion, and depth of osteoarthritic changes in the patella.

PURPOSE

The aim of this study was to determine the prevalence, type of lesion, and depth of osteoarthritic (OA) changes in the patella.

METHODS

One hundred and forty-six cadaveric knees were included in this study with an median age of 83 years (54-97). Patella OA lesion was classified using Han's method: Type 1, no or minimal lesion; Type 2, medial facet lesion without involvement of the ridge; Type 3, lateral facet lesion without involvement of the ridge; Type 4, lesion involvement of the ridge; Type 5, medial facet lesion with involvement of the ridge, Type 6, lateral facet lesion with involvement of the ridge; and Type 7, Global lesion. The depth of OA evaluation was performed following Outerbridge's classification.

RESULTS

OA lesions were observed as follows: (Type 1) 31%, (Type 2) 16%, (Type 3) 3%, (Type 4) 12%, (Type 5) 22%, (Type 6) 2%, and (Type 7) 14%. Outerbridge's classification of over Grade 2 OA depth was observed in 63.7% of subjects. A significant difference of patella OA type in gender was observed. Severe patella OA occurred in female subjects. Greater depth of OA was observed in Types 5 and 7. Most OA occurred in the medial facet of the patella including the ridge. Isolated OA in the lateral facet of the patella was observed in only 2% of all knees.

CONCLUSION

There is a risk of patella OA in female subjects. Patella OA occurred mainly on the medial side. Isolated OA in the lateral facet of the patella was rare. 63.7% of subjects had patella OA.

LEVEL OF EVIDENCE

Controlled laboratory study, Level III.