460 THE INFERIOR EXTREMITY 



backwards and readily breaks through the thin compact bone 

 (cortex) of the popliteal surface of the femur, giving rise to a 

 popliteal abscess. Tuberculous disease originating in the distal 

 part of the femoral diaphysis rarely involves the knee-joint, 

 since in the first place, it is extra-capsular ; and in the second 

 place, it finds less difficulty in spreading to the popliteal fossa 

 than in passing through the epiphysis to gain the joint. If, 

 however, the disease spreads forwards and breaks through the 

 periosteum, it infects the supra-patellar bursa and then involves 

 the joint. 



When tuberculous disease originates in the proximal end of 

 the tibial diaphysis it is entirely extra-capsular, and it commonly 

 spreads distally along the shaft. It may, however, penetrate 

 the periosteum and infect the soft parts on the posterior or 

 lateral aspects, or cause a subcutaneous abscess on the medial 

 aspect. Very rarely the disease may break through the articular 

 cartilage and infect the proximal tibio-fibular joint. Should 

 this joint cavity communicate with the knee-joint through the 

 popliteus bursa (p. 449), the knee-joint itself will be secondarily 

 infected. 



When the patella is the primary site of tuberculous disease, 

 spread to the knee-joint is likely to occur, since only the articular 

 cartilage intervenes. 



The Surgical Approach to the Knee- Joint. The 

 route chosen in any particular case depends partly on the area 

 of the joint which is involved and partly on the ultimate aim 

 of the operation. The age of the patient, too, may have some 

 influence in determining the procedure to be adopted. 



Drainage is difficult to obtain in suppurative arthritis owing 

 to the complicated arrangement of the synovial membrane. 

 Incisions may be made midway between the margin of the 

 femoral condyle and the margin of the patella, on each side, in 

 order to allow a tube to be passed across the joint. From the 

 medial opening a director may be passed backwards across the 

 medial surface of the medial condyle of the femur just below 

 the attachment of the tibial collateral ligament. The point of 

 the instrument is cut down upon when it reaches the posterior 

 synovial pouch (p. 462). A similar proceeding can be carried 

 out on the lateral side, and, finally, an incision should be made 

 into the proximal part of the supra-patellar bursa. Through 

 these various incisions tubes may be arranged so as to provide 

 adequate drainage. 



