This paper describes experimental mapping of lubricating film thickness and mechanism of its forming in contact of CoCrMo femoral head with a diameter of 28 mm and a glass disc with presence of bovine serum as a substitute of synovial fluid occurred in a natural joint. The contact area was illuminated by a xenon lamp and recorded by a high-speed camera. The load applied to the contact area was 5 N corresponding with the contact pressure of 271 MPa. Obtained data was evaluated by a thin film colorimetric interferometry. A pure rolling and partial sliding measurements were examined. From observed interferograms is apparent the deposition of proteins to the glass disc and femoral head surfaces, denaturation and formation of protein aggregations affecting the residual lubricating film thickness. The basic mechanisms of protein film forming were brought out and it is apparent that forming of protein lubricating film is a complex mechanism containing more influences.