PATELLA ( Lat.. small pan or dish, kneepan, patella). or KNEE-CAP. A sesamoid bone. devel oped in the common tendon of the rest us, rest us 61'1(111,1s, and cast us int r mu us great extensor muscles of the leg. it is of rounded. somewhat form, the broad end being directed upward and the apex ward. The anterior or external surface is con vex, perforated by small apertures for the trance of vessels, and marked by rough tudinal stria.., while the posterior or internal surface is smooth and divided into two facets ? by a vertical ridge, which corresponds and fits into the groove on the lower articulating surface of the femur or while the two facets (of which the outer is the broader and deeper) correspond to the articular surface of the two This bone is liable both to dislocation and fracture. Dislocation is rare. It may occur either inward or outward; but it is most quent in the outward direction. The ment may be caused either by external violence. or by too sudden contraction of the extensor muscles in whose conjoined tendon it lies. and is most liable to occur in flabby persons. It may be readily detected by the tation of active motion, and by the bones being felt in its new position: the dislocation is ally capable of being reduced without great culty.
Fracture of the patella may (like dislocation) be caused either by muscular action or by ternal violence. Fracture by muscular action is the more common, and Occurs thus: A per son in danger of falling forward attempts to recover himself by throwing the body backward.
and the violent action of the extensors (chiefly the rectos) snaps the patella across, the upper fragment being drawn up the thigh, while the lower portion is retained in situ by that portion of the common tendon which is continued from the patella to the tubercle of the tibia, and which is called the ligamentum patellae. The conser ? treatment consi,ts in relaxing the ing inuseles by raising the trunk and slightly elevating the limb, which should be kept in a straight position. while straps and other devices are applied directly to the fragments to secure their close approximation. 1 n eonsequence of the great diffieulty of bringing the broken surfaces into exact apposition. it is very difficult to obtain bony reunion of the parts. and the ease generally results either in mere ligamentous union 11r in no true union at all. The practical results in these cases as regards the use of the limb are fairly satisfactory, however.
The operative treatment consists in cutting down on the fragments and fastening them gether with catgut, wire, or S0111e other form of suture. It is attended with reinarkablv teas results, but is not devoid of A measure intermediate between operative and operative treatment consists in the application of hooks or other devices which seize the frag ments through the skin and hold them in apposi tion until union has taken place.