326 capped knee. 



Capped Knee. 



Name. — If a comparison be made between the account about 

 to be given of the nature of capped knee and the pathological 

 descriptions already given of capped hock and capped elbow, 1 

 think 1 shall be fully borne out in the appropriateness of a similar 

 appellation. Similarity of structure entails similarity of disease ; 

 added to which, in the present case, there exists, as we shall here- 

 after find, similarity of causation. 



Definition. — A capped knee is an uniform sweUing of the fore 

 part of the knee, having a soft elastic feel, and evincing, so long 

 as it be recent, more heat than the surrounding skin, though 

 pressure fails to shew that it is any wise or any where painful or 

 even tender. 



Pathology. — When we come to remove the skin from the fore 

 part of the knee, in its normal state, we disclose a layer of dense cel- 

 lular tissue, covering the extensor tendons for the purpose of protec- 

 tion against the " bangs and blows" to which in this exposed situa- 

 tion they are particularly obnoxious. Cutting into this tissue, we 

 discover in its middle a sort of spurious bursa, leading upwards into 

 a similar cavity upon the extensor (metacarpi) tendons ; in which in- 

 tervals it is that effused fluid collects whenever the knee becomes the 

 seat of serous abscess, or, in other words, becomes " capped;" and 

 this explains the reason why the swelling, as it often is found to 

 do, extends upwards upon the arm. The pathology of capped knee 

 is, therefore, extremely simple. Contusion of the part gives rise to 

 either simply increased vascular action in it or to actual inflamma- 

 tion ; its capillary vessels become surcharged with blood, and they 

 relieve themselves by effusion of, commonly, serous fluid, which 

 collects in the interspaces but now described. At the same time, 

 from the circumstance of the fluid not gravitating, but remaining in 

 one place, it is evident that some agglutination of the cellular tissue 

 around must take place, and thatit is contained in a circumscribed sac 

 or cavity. And this sac may, from subsequent distention, through 

 absorption induced by the pressure of the fluid, burst into one of the 

 true hursce mucoscB situated underneath it — most likely into that 

 belonging to the tendon of the extensor metacarpi muscle. When 



