1. Re: Response to Drs Marijnissen and Lafeber, this issue
Ernst B Hunziker, MD 
Osteoarthritis and Cartilage 
Volume 11, Issue 4, Pages (April 2003)
DOI: /S (02)

2. Fig. 1
(A) In a normal joint, a wide gap is visible radiographically between the bony ends, this space being occupied by the opposing layers of articular cartilage tissue, which are X-ray lucent. (B) In this advanced-stage osteoarthritic joint, the articular cartilage layer covering each bony end has been completely worn away. The opposing bony ends are consequently forced together [see (S)], such that no gap is visible between them radiographically. The length of each bone (L) remains the same as in (A). (C) Contact between the bony ends of an arthritic joint leads to the necrosis and lysis of osseous tissue. This degenerative process is followed by an unsuccessful repair response, which is represented by the formation of fibrous connective tissue and fibrocartilage (R). This substituted bone tissue has a similar radiographic appearance to that of articular cartilage (i.e., it is visible as a gap between the opposing bony ends), and it is thus commonly conceived to be repaired cartilage. That the phenomenon represents a process of bone substitution rather than one of tissue accretion upon the original bony ends is indicated by a decrease in radiographic bone length (L–R).
Osteoarthritis and Cartilage  , DOI: ( /S (02) )

3. Fig. 2
(A) Articular cartilage layer (N) in a normal human joint [see also Fig. 1 A]. Bar=1mm. (B) In this advanced-stage osteoarthritic human joint, the articular cartilage layer has been completely worn away, leaving the eburnated (sclerotic) bony tissue (E) directly exposed to the joint space (▾) [see also Fig. 1 B]. Bar=250μm. (C) Contact between the bony ends of this arthritic human joint has led to the necrosis and lysis (D) of osseous tissue. This degenerative process has been followed by an unsuccessful repair response, which is represented by the formation of fibrous connective tissue and fibrocartilage (R) [see also Fig. 1 C]. Bar=500μm.
Osteoarthritis and Cartilage  , DOI: ( /S (02) )