284 



THE ARTIC ULA TIONS 



Fig. 315. — Ligamenttjm Teres, drawn Tight in Flexion Combined with Lateral 



Rotation and Adduction. 



Extensors. — The gluteus maximus, the posterior fibres of the glutei medius and minimus, the 

 biceps, the semitendiiiosus, the semimembranosus, and the ischial fibres of the adductor magnus; 

 also (slightly) the piriformis, obturator internus and gemelli. Abductors. — Gluteus maximus 

 (upper fibres), tensor fasciae latse, gluteus medius, gluteus minimus, and, when the joint is 

 fiexed, the piriformis, obturator internus, the gemelli, and the sartorius also become abductors. 

 Adductors. — Adductores magnus, longus, brevis, and minimus, semitendinosus, biceps, the 

 gracilis, the pectineus, the quadratus femoris, and the lower fibres of the gluteus maximus. 

 Medial rotators. — Psoas (slightly), adductor magnus, semimembranosus, the anterior fibres 

 of the gluteus rnedius and minimus, and the tensor fasciaB latse. Lateral rotators. — Gluteus 

 maximus, posterior fibres of gluteus medius and minimus, the adductors, obturator externus, 

 quadratus femoris, obturator internus, the gemelli, and the piriformis when the joint is extended. 



2. THE KNEE-JOINT 



Class.— Diarthrosis. 



Subdivision. — Ginglymus. 



The knee is the largest joint in the body. It is rightly described as a gingly- 

 moid joint, but there is also an arthrodial element; for, in addition to flexion and 

 extension, there is a sliding backward and forward of the tibia upon the femoral 

 condyles, as well as slight rotation round a vertical axis. It is one of the most 

 superficial, and, as far as adaptation of the bony surfaces goes, one of the weakest 

 joints, for in no position are the bones in more than partial contact. Its strength 

 lies in the number, size, and arrangement of the ligaments, and the powerful 

 muscles and fascial expansions which pass over the articulation and enable it to 

 withstand the leverage of the two longest bones in the body. It may be said'to 

 consist of two articulations with a common synovial membrane — the patello- 

 femoral and the tibio-femoral, the latter being double. It is composed of the 

 condyles and trochlear surface of the femur, the condyles of the tibia, and the 

 patella, united by the following ligaments, which may be divided into an external 

 and internal set: — 



External 



Fibrous expansion of the extensors. 

 Articular capsule. 

 Oblique popliteal ligament. 

 Fibular collateral. 

 Tibial collateral. 



(1) 

 (2) 

 (3) 

 (4) 

 (5) 

 (6) Ligamentum patellar 



Internal 



(1) Anterior crucial. 



(2) Posterior crucial. 



(3) Medial meniscus. 



(4) Lateral meniscus. 



(5) Coronary. 



(6) Transverse. 



