ARTICULATIONS 327 



capsule with accessory thickenings. The lower joint is a 

 syndesmosis, the tibiofibularis syndesmosis, but in some cases 

 a prolongation of the cavity of the ankle-joint projects 

 between the distal ends of the tibia and fibula. The inter- 

 osseous membrane which occupies the interval between the 

 bodies of the bones may be regarded as a ligament common 

 to both joints. 



Dissection. Preparatory to the examination of the tibio-fibular joints the 

 foot must be removed by dividing the ligaments on the medial and lateral 

 aspects of the ankle-joint. The muscles must also be detached from both 

 aspects of the interosseous membrane and the bones of the leg. The 

 ligaments may now be defined. 



Membrana Interossea Cruris (Interosseous Membrane). 



This is a strong membrane which stretches across the interval 

 between the two bones of the leg, and greatly extends the 

 surface for the origin of muscles. It is attached on the one 

 hand to the interosseous border of the tibia, and on the other 

 to the interosseous border of the fibula. It is composed of 

 strong oblique fibres, which take a direction distally and 

 laterally from the tibia to the fibula. An oval opening in its 

 proximal part, immediately distal to the lateral condyle of the 

 tibia, is present for the passage of the anterior tibial vessels, 

 whilst a small aperture, a short distance above the ankle-joint, 

 marks the point where the membrane is pierced by the 

 ramus perforans of the peroneal artery. 



Articulatio Tibiofibularis (O.T. Superior Tibio-fibular Joint). 

 At this joint the bones are held in apposition by a capsule 

 which is strengthened anteriorly and posteriorly. The fibres 

 of the anterior and posterior strengthening bands pass distally 

 and laterally from the lateral condyle of the tibia to the head 

 of the fibula. The posterior band is the weaker of the two, 

 and the tendon of the popliteus with its synovial investment 

 rests upon its upper part. This investment is a prolongation 

 from the synovial membrane of the knee-joint, and in some 

 cases it will be found to be directly continuous with the 

 synovial membrane of the capsule of the tibio-fibular joint. 



The relation of the tendon of the biceps femoris to this 

 joint must not be lost sight of. Attached for the most part 

 to the head of the fibula, its fibres stretch over the front of 

 the joint. Some of its tendinous fibres also obtain insertion 

 into the lateral condyle of the tibia. Firm support is in this 

 way contributed to the tibio-fibular joint. 



