THE STIFLE JOINT 



197 



posterius menisci lateralis) is inserted at the popliteal notch, the upper (Ligamentum femorale 

 menisci lateralis) in a small fossa in the extreme posterior part of the intercondyloid fossa. 



The joint capsule is attached to the margin of the tibial articular surface, 

 but on the femur the line of attachment is for the greater part about half an inch 

 from the articular margin. It is also attached to the convex borders of the semi- 

 lunar cartilages and to the crucial ligaments. It is strong posteriorly, but in front 

 it practically consists only of the synovial layer. There are two synovial sacs, 

 corresponding to the double nature of the articular surfaces; they do not usually 

 communicate, and each is partially divided into an upper and a lower compartment 

 by the semilunar cartilage. The inner sac pouches upward about half an inch 

 over the condyle of the femur. The external sac invests the tendon of origin of the 

 popliteus muscle, and also pouches downward about three or four inches (ca. 8 

 to 10 cm.) beneath the peroneus tertius and long extensor muscles (Fig. 156). 



Internal femoro-patellnr 

 ligament 



Internal lateral {femoro 

 tibial) ligament 



- Accessory cartilage of patella 



Internal ridge of trochlea of 



femur 

 Internal patellar ligament 



Middle pa tella r I iga mcnt 



— Tuberuisily of tibia. 



Fig. 160. — Left Stifle Joint of Horse, Ixterxal Vif.w in- Extreme Extension.^ 

 18, Femur; 20, patella (base); 21, tibia; d, internal semilunar cartilag3. (After EUenberger-Baum, Anat. fiir 



Kiinstler.) 



As stated above, the outer sac sometimes communicates with the femoro-patellar 

 joint cavity, and the inner sac usually, if not always, does so in the adult. 



Ligaments. — There are four of these — two lateral and two crucial. 



The internal lateral ligament (Ligamentum coUaterale tibiale) is attached 

 above to the prominent internal epicondyle of the femur, and below to a rough 

 area below the margin of the internal condyle of the tibia. 



The external lateral ligament (Ligamentum collaterale fibulare) is somewhat 

 thicker; it arises from the upper depression on the external epicondyle, and ends 

 on the head of the fibula. It covers the tendon of the origin of the popliteus 

 muscle, and a bursa is interposed between the lower part of the ligament and the 

 margin of the external condyle of the tibia. 



In this figure the patella is pushed up above the trochlea — a position which it does not 

 occupy normally. 



