The ligaments of the hip-joint are :

1.   Capsular,                                   3. Cotyloid,

2.   Ligamentum teres,                    4. Transverse.

The capsular surrounds the joint : it is attached to the acetabulum, to the innominate bone outside the rim of the cavity, to the cotyloid and transverse ligaments.

Fig. 52.—Back of Foot (Right).

1, Os calcis : 2, astragalus ; 3, head of astragalus ; 4, scaphoid ; 5, middle cuneiform ; 6, inner cuneiform ; 7, outer cuneiform ; 8, cuboid ; 9, metatarsal bones ; 10, phalanges.

Thickened portions of the capsular are called accessory ligaments. They are :

1.   Ilio-femoral,                                3. Ischio-capsular,

2.  Pubo-femoral,                             4. Zonular band.

These, as their names imply, pass from (a) the ilium, (b) the pubis, (c) the ischium to the femur. The last partially encircles the neck of the femur.

The ligamentum teres is inter-articular ; it is attached to a depression in the centre of the head of the femur by one end ; the other end, which divides in two, is fixed to the margins of the notch in the acetabulum, and to the transverse ligament.

The cotyloid ligament surrounds the brim of the cavity, bridges over the notch, closely fits the head of the femur, and acts as a sucker.

The transverse ligament is continuous with the cotyloid, and crosses the notch in the bone, leaving a small opening for bloodvessels and nerves.

Synovial Membrane.—There is a pad of fat at the bottom of the acetabulum, covered by synovial membrane, which also invests the ligamentum teres and covers both surfaces of the cotyloid ligament ; it lines the interior of the capsules, and covers the head of the femur.

Bursas.—There are three bursae in connection with the gluteus maximus muscle, one between the fascia lata, into which the muscle is inserted, and the great trochanter of the femur ; the second is immediately below this ; the third is between the muscle and the tuberosity of the ischium.

There is a bursa between the tendon of the obturator internus and the small sciatic notch.

The blood-supply of the joint is from the circumflex and obturator arteries. The nerve-supply is from great sciatic, obturator, and anterior crural nerves.

The ligaments of the knee-joint are, on the exterior :

1.   The capsular,                        3. Ligamentum patella,

2.   Two lateral,                         4. Posterior ligament.

These ligaments completely invest the joint.

The external lateral ligament is attached to the outer tuberosity of the femur, and to the head of the fibula, below the styloid process.

The internal lateral ligament is attached to the inner tuberosity of the femur, and below the inner tuberosity of the tibia.

The capsular ligament fills up the intervals between the lateral and anterior ligaments.

The ligamentum patellae is attached to the lower border of the patella and the anterior tubercle of the tibia. It is the final insertion of the quadriceps extensor of the thigh.

The posterior ligament is a broad fibrous band which covers the back of the joint. It is attached to the condyles of the femur and to the back part of the head of the tibia.

The crucial ligaments, so called because they form a X, are within the joint. The anterior crucial ligament arises from the upper surface of the tibia in front of the spine, and is attached •to the back part of the external condyle of the femur. The posterior crucial ligament arises from the upper surface of the tibia behind the spine, and is attached to the front part of the internal condyle. In flexion of the knee the posterior ligament tightens, in extension the anterior tightens.

Semilunar Cartilages.—Between the femur and the tibia, and attached to the latter, are two plates of fibro-cartilage, called, from their shape, semilunar ; the horns of each crescent are fixed to the upper surface of the tibia. The two crescents are united by a fibrous band, called the transverse ligament, and the cartilages are held to the tibia by the coronary ligaments.

The synovial membrane is the largest in the body ; it covers both surfaces of the semilunar cartilages, partly invests the crucial ligaments, lines the ligaments on the outside of the joint, and is prolonged for about an inch above the joint on the femur, and below it on the back of the tibia. There is a small bursa between the ligamentum patellae and the anterior tubercle of the tibia, a larger one on the front of the femur above the patella, and others in the neighbourhood of the joint.

The blood-supply is from branches of the popliteal artery.

The nerve-supply is from the anterior crural, external and internal popliteal, and the obturator nerves—ten branches in all.

The ligaments of the ankle-joint are :

1. Anterior.                            3. Internal lateral.

2. Posterior.                           4. External lateral.

The anterior and posterior ligaments are attached in front and behind to the articulating surfaces of the tibia and the astragalus.

The internal lateral passes from the inner malleolus to the astragalus, os calcis and scaphoid.

The external lateral passes from the outer malleolus to the astragalus and os calcis. Synovial membrane lines these ligaments and passes a little way up between the bones of the leg.

A bursa lies between the tendo Achillis and the upper part of the back of the os calcis.

A strong membrane stretches between the tibia and fibula, as between the bones of the arm.

The two principal movements of the ankle-joint are flexion (dorsi-flexion) and extension (plantar flexion). Movements of abduction, adduction and circumduction can be made by extending the foot. These movements are more limited than in the wrist, because the bones of the ankle fit more closely.

The tibia and fibula articulate with each other at their upper and lower extremities. Each articulation has its own ligaments and synovial membrane.

The tarsal and metatarsal bones are bound together by interosseous, plantar, and dorsal ligaments. The two most important in preserving the arch of the foot are the inferior calcaneo-scaphoid, and the two plantar calcaneo-cuboid ; as their names imply, they are attached to the heel-bone and to the scaphoid and cuboid ; the long plantar calcaneo-cuboid is also attached to the three middle metatarsal bones.

The transverse metatarsal ligament stretches across the heads of the metatarsal bones as the corresponding ligament does in the hand.

The anterior annular ligament of the ankle consists of two parts. The upper part stretches across the front of the leg and is attached to the tibia and fibula ; the lower part is over the joint and is attached externally to the anterior of the os calcis, and internally to the inner malleolus and inner margin of the foot.

The internal annular ligament bridges over the hollow between the os calcis and inner malleolus.

The external annular ligament bridges over the hollow between the os calcis and the outer malleolus. The blood-supply is from the posterior tibial artery. The nerve-supply is from the anterior tibial nerve.

The muscles chiefly concerned in producing movements of the joints of the lower limb are as follows :

Hip.

Flexion : iliacus, psoas, pectineus

Extension : gluteus maximus and medius.

Abduction : upper part of gluteus maximus, medius, and minimus.

Adduction : adductors magnus longus and brevis, pectineus, lower part of gluteus maximus, obturator externus.

Rotation inward : anterior part of gluteus medius, anterior part of gluteus minimus, tensor fascia femoris, ilio-psoas.

Rotation outward : obturators, gemelli, pyriformis, gluteus maximus.

Knee.

Flexion : biceps, popliteus, sartorius, gracilis, semitendinosus, semimembranosus.

Extension : extensor quadriceps.

Ankle.

Flexion : tibialis anticus, peroneus tertius. Extension: gastrocnemius, soleus, tibialis posticus, peroneus longus and brevis, plantaris.

Toes.

Flexion : flexors longus and brevis digitorum and pollicis, and lumbrical and interosseous muscles.

Extension: extensors longus and brevis digitorum and pollicis, and lumbrical and interosseous muscles.

Inversion of foot : tibialis anticus, tibialis posticus.

Eversion of foot : the three peronei.

Muscles which extend the foot are on the back and outer aspect of the leg ; those which flex the foot are on the front of the leg.

Fig. 53.—Muscles of Thigh (Anterior View).

1, Tensor fascia femoris; 2, ilio-tibial band; 3, vastus externus;4, gracilis ; 5, sartorius ; 6, rectus femoris ; 7, vastus internus ;8, ligamentum patella; 9, iliacus; 10, psoas ; 11, pectineus ;12, adductor brevis ; 13, adductor longus; 14, adductor

Fig. 54.—Muscles of Thigh (Posterior View).

a, Gluteus maximus ; 2, vastus externus ; 3, biceps ; 4, semitendinosus ; 5, semimembranosus ; 6, popliteal space ; 7, gas trocnomius; 8, gluteus medius ; 9, gracilis ; 10, sartorius.

Fig. 55.—Muscles of Leg (Anterior View).

1, Vastus externus ; 2, vastus internus ; 3, tibialis anticus ; 4, peroneus longus ; 5, tendons of ext. longus digitorum ; 6, peroneus tertius ; 7, peroneus brevis ; 8, ext. longus pollicis; 9, annular ligament ; 10, tibia ; 12, tendons of ext. brevis digitorum ;. 13, soleus.

Fig. 56.—Superficial Muscles of Calf of Leg.

1. Biceps ; 2, semitendinosus ; 3, semimembranosus; 4, gastrocnemius; 5, tendo Achillis ; 6, soleus; 7, popliteal space; 8, flexor longus digitorum; 9, flexor longus hallucis; 10, tendon of peroneus longus.

The muscles which extend the leg are on the front of the thigh ; those which flex it are on the back and inner side of the thigh.

The adductors of the thigh are on the inner aspect.

The muscles which flex the thigh arise in the pelvis and have insertion into the lesser trochanter ; those which extend the thigh are on the back and front of the ilium and sacrum, and are inserted into the great trochanter.