Magnetic resonance imaging (MRI)

Preoperatively, within 6 weeks before TKA, patients had a MRI scan of the affected knee joint. MR images were obtained using a 3.0 Tesla MRI scanner with a maximum gradient amplitude of 40 mT/m (Siemens Magnetom Trio ®, Siemens AG, Erlangen, Germany). The following protocols were used: a transversal T2-weighted 3D CISS (Constructive Interference in Steady State), a sagittal 3D GRE (Gradient recalled Echo), and a sagittal 3D DESS (Dual Echo Steady State).

The severity of OA was estimated by using MRI scans by two board-certified radiologists (E.T., H.S.) using a semi-quantitative scoring system published by Yuslih et al. [15]. The scores are between 1 and 4, with 4 indicating an advanced stage of OA. Moreover, the integrity of both the medial and the lateral menisci was also assessed by MRI scanning. Menisci were defined either as “intact meniscus” (degenerative, but normal structure) or “non-intact meniscus” (luxated or subluxated).