Speaker A
The bones of the crus consist of the tibia and the fibula. The tibia is a long bone consisting of proximal and distal epiphyses and a diaphysis. On its proximal epiphysis, the tibia has two condyles. The lateral condyle, condylus lateralis, and the medial condyle, condylus medialis. These condyles form the proximal articular surface, facies articularis proximalis. This articular surface articulates with the articular surface of the femoral condyles. The condyles are separated by the popliteal notch, incisura poplitea, and the intercondylar eminence, eminentia intercondylaris. The intercondylar eminence consists of lateral and medial intercondylar tubercles, tuberculum intercondylare laterale et mediale. Cranial to the intercondylar eminence lies the cranial intercondylar area, area intercondylaris cranialis. It is divided into two rough surfaces for the attachment of the menisci. In the center of the intercondylar eminence lies the central intercondylar area, area intercondylaris centralis, for the attachment of the cranial cruciate ligament. Caudal to this eminence lies the caudal intercondylar area, area intercondylaris caudalis, for the attachment of the caudal cruciate ligament and the medial meniscus; on the caudolateral aspect of the lateral condyle lies the articular surface for articulation with the fibula, facies articularis fibularis, and distal to the condyles lies the tibial tuberosity, tuberositas tibiae. In the center of this tuberosity runs the groove of the tibial tuberosity, sulcus tuberositas tibiae. Lateral to the tibial tuberosity lies the extensor groove, sulcus extensorius, for the digital extensor muscles. The body of the tibia, corpus tibiae, has three borders and three surfaces. The borders. The cranial border, margo cranialis, formerly known as the tibial crest, extends proximally into the tibial tuberosity. The medial border, margo medialis, and the lateral border, margo lateralis. This border is often called the interosseous border, margo interosseus, as it faces the interosseous space between the tibia and fibula. Between the borders lie the surfaces. The lateral surface, facies lateralis, the medial surface, facies medialis, and the caudal surface, facies caudalis. On the caudal surface, there is the popliteal line, linea musculi poplitei. This line separates the surface for the attachment of the popliteus muscle from the surface for the attachment of the digital flexor muscles. On the distal epiphysis of the tibia lies the tibial trochlea or cochlea, cochlea tibiae. The trochlea consists of grooves delimited by ridges. The trochlea is required for articulation with the tarsal bones. On the trochlea, there is a medial thickening called the medial malleolus, malleolus medialis. On the medial malleolus, caudally, lies the malleolar groove, sulcus malleolaris. On the lateral side of the tibial trochlea, there is an identical thickening called the lateral malleolus, malleolus lateralis. It also has a groove. The fibula of the crus is reduced, as the tibia bears the main load. The fibula consists of the head, caput fibulae, with the articular surface of the fibular head, facies articularis capitis fibulae, the neck, collum fibulae, and the body, corpus fibulae; to determine if the crus is right or left, note that the fibula and the extensor groove are directed laterally, and the tibial tuberosity cranially. The popliteal notch is located caudally. Thus, this is the right crus. In the horse, the medial intercondylar tubercle is higher than the lateral one. On the tibial trochlea, the grooves are positioned obliquely. The fibula is reduced. Only the proximal part remains. In cattle, the medial intercondylar tubercle is higher than the lateral one. There are three straight grooves on the trochlea of the tibia. The smallest of them, located laterally, is intended for articulation with the malleolar bone in cattle. Above it lies the notch for the fibula, the fibular notch (incisura fibularis). It is also designed for articulation with the malleolar bone. The fibula is reduced. The head of the fibula is completely fused with the lateral condyle of the tibia. The body of the fibula is absent. The distal part of the fibula forms the malleolar bone (os malleolare). On the malleolar bone, the malleolar groove (sulcus malleolaris) is located laterally. The malleolar bone, with its articular surface (facies articularis malleoli), fits into the lateral groove of the tibia and the notch. The tibia is short and massive. The lateral intercondylar tubercle is higher than the medial one. The fibula is long and flattened like a ribbon. The proximal part is wider than the distal one. The distal part of the fibula forms the lateral malleolus. The lateral malleolus has an articular surface for articulation with the tibia and the proximal row of tarsal bones. The grooves on the trochlea of the tibia are positioned straight. In dogs, the intercondylar tubercles of the tibia are small and of equal height. The grooves on the trochlea of the tibia are positioned straight. The fibula is thin, long, and spirally twisted. Because of this, its body is shaped like a groove. The distal part of the fibula forms the lateral malleolus.
