Comment on some surface characteristics of articular cartilage—I a scanning electron microscopy study and a theoretical model for the dynamic interaction of synovial fluid and articular cartilage V. C. Mow, W. M. Lai and I. Redler and some surface characteristics of articular cartilage—II on the stability of articular surface and a possible biochemical factor in etiology of chondrodegeneration V. C. Mow, W. M. Lai, J. Eisenfeld and I. Redler