ABNORMAL CONDITIONS OF THE KNEE-JOINT. 



65 



Abscess may, however, form in the interior 

 of the heads of the tibia or lower extremity of 

 the femur without being preceded by the death 

 of any portion of the bone, as is proved by a 

 specimen in the museum of the Richmond 

 Hospital. A child, aged about twelve, had 

 long suffered from chronic disease of the upper 

 portion of the tibia. A chronic symptomatic 

 abscess pointed and opened spontaneously in 

 the popliteal space, and here a fistulous open- 

 ing remained discharging a quantity of thin 

 sanious pus. While under treatment for this 

 chronic disease, a sudden attack of acute ar- 

 thritis set iu, which threatened the patient's 

 life, and amputation was immediately per- 

 formed. Upon examination of the knee-joint 

 and of the interior of the bones, which were 

 exposed by a vertical section made from before 

 backwards, an abscess was discovered in the 

 centre of the head of the tibia, capable of con- 

 taining a walnut. This communicated with 

 the popliteal abscess, which had long had a 

 fistulous opening in the ham ; but the abscess 

 in the interior of the tibia was now found to 

 have another opening into the cavity of the 

 knee-joint, which had all the appearance of 

 having been quite recent. The matter of the 

 abscess of the tibia having suddenly made 

 its way into the cavity of the knee-joint was the 

 immediate exciting cause of the acute arthritis 

 genu, evidences of which were seen in a layer 

 of lymph which invested the synovial mem- 

 brane and the cartilages. The patient ulti- 

 mately recovered. 



When the chronic form of necrosis affects 

 the tibia and the epiphysis is included in the 

 disease, the knee-joint sometimes remains but 

 little altered, but in other cases remarkable 

 changes in its form take place. The leg is 

 sometimes fully extended, and is even in ad- 

 vance of the natural line, but it is more gene- 

 rally flexed on the femur, and the tibia is at 

 the same time somewhat curved into the form 

 of an arch, the concavity looking forwards. We 

 have frequently known displacement of the su- 

 perior head of the tibia, where it enters into the 

 formation of the knee-joint, to take place back- 

 wards towards the popliteal space. This dis- 

 placement is usually incomplete. We have 

 examined many living examples of this defor- 

 mity, and have had a few opportunities of inves- 

 tigating the anatomical changes the joint has 

 been subjected to. 



Many circumstances tend to influence the 

 direction in which the luxation may take place. 

 The position in which the limb is preserved 

 during the attack of inflammation of the tibia is 

 one of the most influential. As the limb is 

 generally flexed during the first stage of the 

 disease, the partial luxation backwards will be 

 the one most likely to occur. In these cases, 

 whether the femur or tibia close to the knee be 

 the seat of the necrosis, more or less of effusion 

 takes place into the synovial sac of the knee- 

 joint ; all the ligaments of the joint become 

 softened and relaxed; and the action of the 

 hamstring muscles overcomes the resistance of 

 any remaining structures, and the tibia is dis- 

 located partially backwards. 



VOL. III. 



Mr. West, surgeon to the Longford Infir- 

 mary, sent to the writer of this article the leg 

 and knee-joint of a man who had long con- 

 tended against the consequences of a chronic 

 necrosis of the tibia. There were from time to 

 time exfoliations of bone, and a continual dis- 

 charge of a thin sanious matter which so re- 

 duced the strength of the patient as to render 

 amputation necessary. A cast of the limb, taken 

 by Mr. Smith, and the bone are preserved in 

 the museum of the Richmond Hospital, (Jigs. 

 4 and 5,) from which it will be observed that the 



Fig. 4. 



Displacement of the tibia backwards from necrosis. 



displacement of the head of the tibia was par- 

 tially backwards. This bone was drawn also 

 somewhat upwards, passing inferiorly so far 

 round the condyles of the femur that the arti- 

 cular surfaces were almost abandoned. This 

 is the simplest form of displacement of the 

 tibia at the knee-joint from disease which we 

 have noticed as the result of a chronic process 

 of necrosis. We have seen some instances of 

 necrosis in which the whole leg and foot were 

 greatly rotated outwards on the femur, so that 

 the inner ankle was placed directly forwards, 

 and the outer malleolus directly backwards. In 

 these cases the patella is completely dislocated 

 on the outer condyle of the femur (Jig. 6), be- 

 cause the tubercle of the tibia, in its movement of 

 rotation outwards, carries with it the ligamentuin 



F 



