Table 2 The histological results of all treatment groups, assessed according to cellular morphology, GAG staining and repair tissue surface

Empty chondral defect (Fig. 3a)

Mixture of fibrous tissue and fibrocartilage

Negative

Smooth, but depressed

Autologous cartilage chips (Fig. 3e)

Predominantly fibrocartilage. Areas with hyaline-like tissue dispersed throughout the defect area

Negative

Smooth

MFx (Fig. 3c)

Fibrocartilage

<50 %

Smooth, but depressed

MACI (Fig. 3d)

Hyaline cartilage in the periphery, fibrocartilage in the center

Negative

Smooth, but depressed

Empty osteochondral defect (Fig. 3b)

Predominantly fibrous tissue. Fibrocartilage present profoundly. Rich vascularity

<10 %

Smooth, but depressed

Autologous bone graft (Fig. 3f)

Mixture of fibrous tissue and fibrocartilage. Rich vascularity

<50 %

Smooth, but depressed. Slight fissuring observed

ADTT (Fig. 3g)

Hyaline cartilage and fibrocartilaginous tissue profoundly. Fibrocartilage and fibrous tissue superficially

<50 %

Smooth, but slightly depressed