condyle of the femur, and below to the inner tuberosity of the tibia. It is crossed at its lower part by the tendons of the inner hamstring, from which it is separated by a synovial bursa, and it covers in the anterior slip of the semi-membranosus tendon and the inferior internal articular artery.

External lateral ligaments. - The long external lateral ligament is a strong and round cord, which descends from the posterior part of the tubercle on the external condyle of the femur to the outer part of

the head of the fibula.

The short external lateral ligament is an irregular fasciculus situated behind the preceding, arising from the external condyle near the origin of the head of the gastrocnemius muscle, and inserted into the posterior part of the head of the fibula. It is firmly connected with the external semilunar fibro-cartilage, and appears principally intended to connect that cartilage with the fibula; sometimes it is lost supcriorly in the capsular ligament without reaching the femur.'

The long external lateral ligament is covered in by the tendon of the biceps, and has passing beneath it the tendon of origin of the popliteus muscle, and the inferior external articular artery.

The true ligaments within the joint are the crucial, transverse, and coronary.

The anterior, or external crucial ligament, arises from the depression on the head of the tibia in front of the spinous process, and passes upwards and backwards to be inserted into the inner surface of the outer condyle of the femur, as far back as its posterior border. It is smaller than the posterior. The posterior, or internal crucial ligament, arises from the depression on the head of the tibia behind the spinous process, and passes upwards and forwards to be inserted into the [outer surface of the] inner condyle of the femur. This ligament is less oblique and larger than the anterior.

The transverse ligament is a small slip of fibres which extends transversely from the external semilunar fibro-cartilage, near its anterior extremity, to the anterior convexity of the internal cartilage.

neath the internal lateral ligathe internal lateral ligament. 6. Long external lateral ligament. 7. Short external lateral ligament. 8. Tendon of the

ment. 5. Posterior part of

popliteus muscle cut through. 9. Postero-superior tibio-fibular ligament.

The coronary ligaments are the short fibres by which the convex borders of the semilunar cartilages are connected to the head of the tibia and ligaments surrounding the joint. The semilunar fibro-cartilages are two falciform plates of fibro-cartilage, situated on the head of the tibia around its margin, and serving to deepen the surface of articulation for the condyles of the femur. They are thick along their convex border; thin and sharp along their concave edge.

The internal semilunar fibro-cartilage forms an oval cup for the reception of the internal condyle of the femur; it is connected by its convex border with the head of the tibia and internal and posterior ligaments, by means of its coronary ligament; and by its two extremities is firmly implanted into the depression before and behind the spinous process. The external semilunar fibro-cartilage bounds a circular fossa for the external condyle; it is connected by its convex border with the head of the tibia, and to the external and posterior ligaments by

'Professor Retzius considers the short external lateral ligament as part of the tendon of origin of the popliteus muscle.

its coronary ligament; by its two extremities it is inserted into the depression

FIG. 142.

between the two projections which constitute the spinous process of the tibia. The two extremities of the external cartilage being inserted into the same fossa, form an almost complete circle, and the cartilage being somewhat broader than the internal, nearly covers the articular surface of the tibia.

The external semilunar fibro-cartilage, besides giving off a fasciculus from its anterior border to constitute the transverse ligament, is continuous by some of its fibres with the extremity of the anterior crucial ligament; posteriorly it divides into three slips; one, a strong cord, ascends obliquely forwards to be inserted into the anterior part of the inner condyle of the femur in front of the posterior crucial ligament; another is the fasciculus of insertion into the fossa of the spinous process; while the third, of small size, is continuous with the posterior part of the anterior crucial ligament.

THE RIGHT KNEE JOINT LAID OPEN FROM THE FRONT, IN ORDER TO SHOW THE INTERNAL LIGAMENTS. 1. Cartilaginous surface of the lower extremity of the femur with its two condyles; the figure 5 rests on the external; the figure 3 on the internal condyle. 2. Anterior crucial ligament. 3. Posterior crucial ligament. 4. Transverse ligament. 5. Attachment of the ligamentum mucosum; the rest has been removed. 6. Internal semilunar fibrocartilage. 7. External semilunar fibrocartilage. 8. Part of the ligamentum patellæ turned down. 9. Bursa situated between the ligamentum patellæ, and head of the tibia; laid open. 10. Antero-superior tibio-fibular ligament. The synovial membrane of the knee joint 11. Interosseous membrane; the openis by far the most extensive in the body. It ing above this membrane is for the invests the cartilaginous surfaces of the conpassage of the anterior tibial artery. dyles of the femur, head of tibia, and inner surface of the patella; it covers both surfaces of the semilunar fibro-cartilages; and is reflected upon the crucial ligaments, and inner surface of the ligaments which form the circumference of the joint. On each side of the patella it lines the tendinous aponeuroses of the vastus internus and vastus externus muscle, and forms a pouch of considerable size between the extensor tendon and front of the femur. It also forms the folds in the interior of the joint, called "ligamentum mucosum," and "ligamenta alaria." The superior pouch of the synovial membrane is supported and raised during the movements of the limb by a small muscle, the subcrureus, which is inserted into it.

The ligamentum mucosum is a slender conical process of synovial membrane inclosing at few ligamentous fibres which proceed from the transverse ligament. It is connected, by its apex, with the anterior part of the condyloid notch, and, by its base, is lost in the mass of fat which projects into the joint beneath the patella.

The alar ligaments are two fringed folds of synovial membrane, extending from the ligamentum mucosum, along the edges of the mass of fat to the sides of the patella.

Between the ligamentum patellæ and synovial membrane is a considerable mass of fat, which presses the membrane towards the interior of the joint, and occupies the fossa between the condyles.

Besides the proper ligaments of the articulation, the joint is strengthened in front by the fascia lata, which is thicker at the outer than the inner side, by a tendinous expansion from the vastus internus, and some scattered ligamentous fibres inserted into the sides of the patella. This expansion has been termed the capsular ligament.

Actions.

The knee joint is one of the strongest of the articulations of the

body, while, at the same time, it admits of the most perfect degree of movement in the direction of flexion and extension. During flexion the articular surface

LONGITUDINAL SECTION OF THE LEFT KNEE JOINT, SHOWING THE REFLECTIONS OF ITS SYNOVIAL MEMBRANE. 1. Cancellous structure of the lower part of the femur. 2. Tendon of the extensor muscles of the leg. 3. Patella. 4. Ligamentum patellæ. 5. Cancellous structure of the head of the tibia. 6. A bursa situated between the ligamentum patella and head of the tibia. 7. Mass of fat projecting into the cavity of the joint below the patella. ***** The syno. vial membrane. 8. The pouch of synovial membrane which ascends between the tendon of the extensor muscles of the leg, and front of the lower extremity of the femur. 9. One of the alar ligaments; the other has been removed with the opposite section. 10. Ligamentum mucosum left entire; the section being made to its inner side. 11. Anterior or external crucial ligament. 12. Posterior ligament of the joint. The plan of the synovial membrane, which is here presented to the student, is divested of all unnecessary complications. It may be traced from the sacculus (at 8), along the inner surface of the patella; then over the adipose mass (7) from which it throws off the mucous ligament (10); then over the head of the tibia, forming a sheath to the crucial ligaments; then upwards along the posterior ligament and condyles of the femur, to the sacculus whence its examination commenced.

FIG. 143.

of the tibia glides forwards on the condyles of the femur; the lateral ligaments, the posterior, and the crucial ligaments are relaxed; while the ligamentum patella, being on the stretch, serves to press the adipose mass behind it into the vacuity formed in front of the joint. In extension all the ligaments are put on the stretch, with the exception of the ligamentum patella. When the knee is semi-flexed, a partial degree of rotation is permitted.

3. Articulation between the Tibia and Fibula. - The tibia and fibula are held firmly connected by means of seven ligaments, namely,

The anterior superior tibio-fibular ligament is a strong fasciculus of parallel fibres passing obliquely downwards and outwards from the outer tuberosity of the tibia, to the anterior surface of the head of the fibula.

The posterior superior tibio-fibular ligament, thicker and stronger than the anterior, is disposed in a similar manner on the posterior surface of the joint. Within the articulation there is a synovial membrane which is sometimes continuous with that of the knee joint.

The interosseous membrane, or superior interosseous ligament, is a broad layer of aponeurotic fibres which pass obliquely downwards and outwards, from the sharp ridge on the tibia to the inner edge of the fibula, and are crossed at an acute angle by a few fibres taking the opposite direction. The ligament is deficient above, leaving a considerable interval between the bones, through which the anterior tibial artery takes its course forwards to the anterior aspect of the leg; and perforated below, near its lower third, for the anterior peroneal artery and vein.

The interosseous membrane is in relation, in front, with the tibialis anticus, extensor longus digitorum, extensor proprius pollicis, anterior tibial vessels and nerve, and anterior peroneal artery; behind, with the tibialis posticus, flexor longus digitorum, and posterior peroneal artery.

The inferior interosseous ligament consists of short and strong fibres, which hold the bones firmly together inferiorly, where they are nearly in contact. This articulation is so firm, that the fibula is broken when an attempt is made to rupture the ligament.

The anterior inferior tibio-fibular ligament is a broad band, consisting of two fasciculi of parallel fibres which pass obliquely across the anterior aspect of the articulation of the two bones at their inferior extremity, from tibia to fibula.

The posterior inferior tibio-fibular ligament is a similar band on the posterior surface of the articulation. Both ligaments project somewhat below the margin of the bones, and serve to deepen the cavity of articulation with the astragalus. The transverse ligament is a narrow band of ligamentous fibres, continuous with the preceding, and passing transversely across the back of the ankle joint, between the two malleoli.

The synovial membrane of the inferior tibio-fibular articulation, is a duplicature of the synovial membrane of the ankle joint, reflected upwards for a short distance between the two bones.

Actions. - Between the tibia and fibula there exists a slight degree of movement, which is calculated to enable the latter to resist injury by yielding for a trifling extent to forcible pressure.

4. Ankle Joint. ing into its formation

FIG. 144.

FIG. 145.

The ankle is a ginglymoid articulation; the surfaces enter-
are the under surface of the tibia with its malleolus
and the malleolus of the
fibula, above; and the
surface of the astragalus
with its two lateral facets,
below. The ligaments
are three in number:

Anterior,

Internal lateral,
External lateral.

INTERNAL VIEW OF THE ANKLE JOINT. 1. Internal malleolus of the tibia. 2, 2. Astragalus. 3. Os calcis. 4. Scaphoid bone. 5. Internal cuneiform bone. 6. Internal lateral or deltoid ligament. 7. Anterior ligament. 8. Tendo Achillis; a small bursa is seen interposed between this tendon and the posterior tuberosity of the os calcis.

The anterior ligament is a thin, membranous layer, passing from the margin of the tibia, to the astragalus, in front of its articular surface." It is in relation, in front, with the tendons of the extensors of the great and lesser toes, tibialis anticus, peroneus tertius, and anterior tibial vessels and nerve. Posteriorly it lies in contact with a stratum of extrasynovial adipose tissue and the synovial membrane The internal lateral or deltoid ligament is a triangular layer of fibres, attached superiorly, by its apex, to the internal malleolus; inferiorly, by an expanded base, to the astragalus, os calcis, and scaphoid bone. Beneath the superficial layer of this ligament is a stronger and thicker fasciculus, which connects the apex of the internal malleolus with the side of the astragalus.

POSTERIOR VIEW OF THE ANKLE JOINT. 1. Lower part of the interosseous membrane. 2. Posteroinferior ligament connecting the tibia and fibula. 3. Transverse ligament. 4. Internal lateral ligament. 5. Posterior fasciculus of the external lateral ligament. 6. Middle fasciculus of the external lateral ligament. 7. Synovial membrane of the ankle joint. 8. Posterior tuberosity of the os calcis.

The internal lateral ligament is covered in and partly concealed by the tendon

of the tibialis posticus, and, at its posterior part, is in relation with the tendon of the flexor longus digitorum, and flexor longus pollicis.

FIG. 146.

The external lateral ligament consists of three strong fasciculi, which proceed from the inner side of the external malleolus, and diverge in three different directions. The anterior fasciculus passes forwards to be attached to the astragalus; the posterior, backwards, to be connected with the astragalus posteriorly; and the middle, longer than the other two, descends to be inserted into the outer side of the os calcis.

"It is the strong union of this bone," says Sir Astley Cooper, "with the tarsal bones, by means of the external lateral ligaments, which leads to its being more frequently fractured than dislocated."

The transverse ligament of the tibia and fibula occupies the place of a posterior ligament of the ankle joint. It is in relation, behind, with the posterior tibial vessels and nerve, and tendon of the tibialis posticus muscle; in front, with the extra-synovial adipose tissue and synovial membrane.

The synovial membrane invests the cartilaginous surfaces of the tibia and fibula (sending a duplicature upwards between their lower ends), and the upper surface and two sides of the astragalus. It is then reflected upon the ante

EXTERNAL VIEW OF THE ANKLE JOINT. 1. Tibia. 2. External malleolus of the fibula. 3, 3. Astragalus. 4. Os calcis. 5. Cuboid bore. 6. Anterior fasciculus of the external lateral ligament attached to the astragalus. 7. Its middle fasciculus, attached to the os calcis. 8. Its posterior fasciculus, attached to the astragalus. 9. Anterior ligament of the ankle.

rior and lateral ligaments, and on the transverse ligament posteriorly.

Actions. The movements of the ankle joint are flexion and extension only, without lateral motion.

5. Articulation of the Tarsal Bones.-The ligaments which connect the seven bones of the tarsus to each other are of three kinds,—

Dorsal,

Plantar,

Interosseous.

The dorsal ligaments are small fasciculi of parallel fibres, which pass from each bone to all the neighboring bones with which it articulates. The only dorsal ligaments deserving of particular mention are, the external and posterior calcaneoastragaloid, which, with the interosseous ligament, complete the articulation of the astragalus with the os calcis; the superior and internal calcaneo-cuboid liga ments; and the superior astragalo-scaphoid ligament. The internal calcaneocuboid, and superior calcaneo-scaphoid ligament, which are closely united posteriorly in the deep groove which intervenes between the astragalus and os calcis, separate anteriorly to reach their respective bones; they form the principal bond of connexion between the first and second range of bones of the foot. It is the division of this portion of these ligaments that demands the careful attention of the surgeon in performing Chopart's operation.

The plantar ligaments have the same disposition on the plantar surface of the foot; three of them, however, are of large size, and have especial names, viz., the

Calcaneo-scaphoid,
Long calcaneo-cuboid,

Short calcaneo-cuboid.

The inferior calcaneo-scaphoid ligament is a broad and fibro-cartilaginous