274 THE ARTICULATIONS. 



II. Knee-joint. 



The knee-joint was formerly described as a ginglymus or hinge-joint, but is 

 really of a much more complicated character. It must be regarded as consist- 

 ing of three articulations in one : one between each condyle of the femur and the 

 corresponding tuberosity of the tibia, which are condyloid joints, and one between 

 the patella and the femur, which is partly arthrodial, but not completely so, since 

 the articular surfaces are not mutually adapted to each other, so that the movement 

 is not a simple gliding one. This view of the construction of the knee-joint receives 

 confirmation from the study of the articulation in some of the lower mammals, 

 where three synovial membranes are sometimes found, corresponding to these three 

 subdivisions, either entirely distinct or only connected together by small communi- 

 cations. This view is further rendered probable by the existence of the two crucial 

 ligaments within the joint, which must be regarded as the external and internal 

 lateral ligaments of the inner and outer joints respectively. The existence of 

 the ligamentum mucosum would further indicate a tendency to separation of the 

 synovial cavity into two minor sacs, one corresponding to each joint. 



The bones entering into the formation of the knee-joint are the condyles of the 

 femur above, the head of the tibia below, and the patella in front. The bones are 

 connected together by ligaments, some of which are placed on the exterior of the 

 joint, while others occupy its interior. 



External Ligaments. Interior Ligaments. 



Anterior, or Ligamentum Anterior, or External Crucial. 



Patellae. Posterior, or Internal Crucial. 



Posterior, or Ligamentum Two Semilunar Fibro-cartilages. 



Posticum Winslowii. Transverse. 



Internal Lateral. Coronary. 



Two External Lateral. Ligamentum mucosum. ^ Processes of Syn- 



Capsular. Ligamenta alaria. j ovial Membrane. 



The Anterior Ligament, or Ligamentum Patellae (Fig. 183), is the central 

 portion of the common tendon of the Extensor muscles of the thigh which is 

 continued from the patella to the tubercle of the tibia, supplying the place of an 

 anterior ligament. It is a strong, flat, ligamentous band about three inches in 

 length, attached, above, to the apex of the patella and the rough depression on its 

 posterior surface ; below, to the lower part of the tubercle of the tibia, its superficial 

 fibres being continuous over the front of the patella with those of the tendon of the 

 Quadriceps extensor. The lateral portions of the tendon of the Extensor muscles 

 pass down on either side of the patella, attached to the borders of this bone and its 

 ligament, to be inserted into the upper extremity of the tibia on each side of the 

 tubercle ; externally, these portions merge into the capsular ligament. They are 

 termed lateral patellar ligaments. The posterior surface of the ligamentum patellae 

 can usually be easily separated from the front of the capsular ligament. 



The Posterior Ligament (Ligamentum Posticum Winslowii) (Fig. 184) is a broad, 

 flat, fibrous band, formed of fasciculi separated from one another by apertures for 

 the passage of vessels and nerves. It is attached, above, to the upper margin of the 

 intercondyloid notch of the femur, and below, to the posterior margin of the head 

 of the tibia. Superficial to the main part of the ligament is a strong fasciculus 

 derived from the tendon of the Semimembranosus, and passing from the back 

 part of the inner tuberosity of the tibia obliquely upward and outward to the 

 back part of the outer condyle of the femur. The posterior ligament forms 

 part of the floor of the popliteal space, and the popliteal artery rests upon it. 



The Internal Lateral Ligament is a broad, flat, membranous band, thicker 

 behind than in front, and situated nearer to the back than the front of the joint. 

 It is attached, above, to the inner tuberosity of the femur ; below, to the inner 

 tuberosity and inner surface of the shaft of the tibia to the extent of about two 

 inches. It is crossed, at its lower part, by the tendons of the Sartorius, Gracilis, 



