Studies on the Anatomy of the Fat Pad Tissues of the Human Knee Joint and Pathohistological Findings of these Tissues in the R. A. Patients

Abstract

Weston and Palmer (1978) recently described their radiological research on the fat pad tissues and their intraarticular location along with their diagnostic value in various disorders of the human knee joint.
As early as 1938 Kling already drew attention to these fat pad tissue and explained their anatomy. The author, while performing knee joint synovectomy, observed clearly the existence of these fat tissues which cover the suprapatellar pouch in every instance.
In spite of such uniformity of the fat tissue in their anatomical location, their nomenclature varies from one textbook to another. For example, some describe their location as being extrasynovial or subsynovial, and others as lying on the synovial capsule of the knee joint.
In this study, the author, using human cadaver specimens, designates these fat pad tissues as being located in 5 different places which are named as follows: 1. infrapatellar fat pad; 2. anterior suprapatellar fat pad; 3. posterior suprapatellar fat pad; 4. fat pad surrounding the patellar margin; 5. popliteal fat pad.
Then, the specimens from infrapatell ar fat pad and ant. and post. suprapatellar fat pads are sectioned, stained and examined using ordinary microscopic techniques so that the location of these fat pad tissues were identified in relation to the surrounding tissues and it was found that the infrapatellar fat pad is located right beneath the synovial lining whereas the ant. and post. suprapatellar fat pads are located in between the tendinous membrane of quadriceps muscle and the layers of collagen fiber bundles running in parallel with the synovia just on the o utside of the subsynovial tissue.
From these findings the aut hor concludes that the suprapatellar pouch, having the tissue structure comprizing both Stratum fibrosum and Stratum synoviale, can be regarded as the joint capsule itself and therefore the suprapatellar fat pad can be interpreted as being extracapsular in nature.
In the second part of the article, the fat pad specimens taken surgically from the rheumatoid arthritic knee joint were studied macroscopically and microscopically.
In gross eye examination fat pads in rheumatoid knee joints were found to be more or less edematously swollen in comparison with the normal joint. In microscopic study, however, findings of various types of angitis and connective tissue inflammation were observed in the interlobular connective tissue of these fat pads.
The connective tissue dividing these fat pad tissues into smaller lobuli is rich in fibers as well as in fibrocyt but is poorly supplied with capillary, and moderately supplied with small vessels which are arterioles and venules. Various kinds of infiltration or proliferation of immunocytes such as lymphocytes and plasma cells surrounding small vessels, capillaries and in the interstitial stroma tissue and also the proliferation of fibroblast, angioblast and collagen fibers in various degree were very common findings in the microscopic specimens in these studies.
In addition, edematous swelling of the stroma and disintegration or segmentation of edematously swollen collagen fiber were seen in the interlobular connective tissue of these fat pads which findings could be interpreted as a tissue response to the recurrent rheumatoid inflammation of the knee joint.
The findings of matured fibrosis formation in the interlobular connective tissue were very rarely seen in this study. The angitis and connective tissue inflammation of various kinds seen in this study can well be interpreted as allergic in nature as well as the evidence of the selfperpetuation mechanism of this disease.
And since these obvious his tological findings of rheumatoid inflammation are abundantly demonstrated, we conclude that in almost every patient fat pad tissue removal in conjunction with knee joint synovectomy seems to be justified in the treatment of R. A.