Oligolamellar nature of the articular surface.

The osmiophilic lining of the articular surface has been studied by electron microscopy and shown to be oligolamellar phospholipid by employing special nondestructive fixation procedures. This finding was confirmed using hydrophobic probes in epifluorescence microscopy and by other simple tests of hydrophobicity. Oligolamellar phospholipid was also observed within the subchondral matrix while lamellar bodies, phospholipid in its most surface-active state, were found in the type of canals which can result from superficial fibrillation. The results are discussed as consistent with a previously proposed hypothesis whereby joints are lubricated by shearing between surface lamellae of phospholipid just as occurs in graphite when writing with a pencil.