1. With the body still in the prone position, note that the iliopsoas muscle lies in front and below, while the short lateral rotators are at the back of the hip joint. Follow the tendon of the obturator externus as it curves upwards and laterally along the back of the neck of the femur deep to the quadratus femoris to reach the trochanteric fossa. Cut the obturator externus.

2. Remove the remaining muscles on the posterior aspect of the hip joint and clean the capsule. Note that the capsule covers only the medial two-thirds of the neck of the femur posteriorly.

3. Turn the body on to its back. Cut the tendon of the iliopsoas just below the hip joint and reflect it. Next examine the anterior part of the capsule and note that it is attached to the intertrochanteric line. Define the iliofemoral ligament extending from the upper margin of the acetabulum to the intertrochanteric line of the femur. Note its two thickened bands, the transverse part and the descending part, attached to the upper and lower ends of the intertrochanteric line respectively.

4. Define the pubofemoral ligament attached above to the superior ramus of the pubic bone adjoining the acetabulum and blending below with the descending part of the iliofemoral ligament.

5. Posteriorly identify the ischiofemoral ligament attached to the ischium below and behind the acetabulum and passing upwards and laterally to fuse with the posterior part of the capsule. Why do the three ligaments of the hip show an increasing degree of twist? When do these ligaments get taut?

6. Open the joint anteriorly by cutting obliquely from above downwards and medially across the capsule.

7. Pull the head of the femur out of the acetabulum and observe that the ligament of the head of femur resists its separation from the acetabulum. Cut the ligament and withdraw the head of the femur from the acetabulum. Note that the fibrocartilaginous acetabular labrum, which is attached to the margin of the acetabulum, also resists the withdrawal of the head of the femur. Why?

8. Identify the acetabular notch on the inferior margin of the acetabulum and note that this notch is bridged across by the transverse ligament. Verify the attachment of the ligament of head of femur passing from a pit in the head of the femur to the margins of the acetabular notch and to the transverse ligament.

9. Cut any remaining structures and free the limb from the pelvis. The lower limb has now been separated from the body.

POPLITEAL FOSSA AND BACK OF THE LEG

1. Make the following incisions:

(a)a vertical incision in the midline of the back of the leg down to the heel; and

(b) a transverse incision connecting the two malleoli across the back of the ankle. Reflect the skin flaps.

2. As you clear away the superficial fascia, you will find several cutaneous nerves. Note that the saphenous nerve accompanies the great saphenous vein on the medial side of the leg.

3. Examine the deep fascia of the leg which forms a complete covering for the musculature of the leg. It also sends septa to the anterior and posterior margins of the fibula thus separating the leg muscles into three compartments, namely the anterior (extensor), lateral (fibular) and posterior (flexor) compartments. Note that the medial surface of the tibia is subcutaneous.

4. Define the flexor retinaculum extending between the medial malleolus of the tibia and the medial process of the tuber calcaneus.

5. Remove the deep fascia behind the knee and trace the hamstring muscles to their insertions. Observe that the biceps femoris tendon is inserted into the head of the fibula together with the attachment of the fibular collateral ligament of the knee joint. Follow the semitendinosus to its insertion into the upper end of the medial surface of the shaft of the tibia behind the insertions of the sartorius and gracilis. Trace the main insertion of the semimembranosus into the groove on the posteromedial aspect of the medial condyle of the tibia. Note that it gives expansions which form the oblique popliteal ligament of the knee and the fascia covering the popliteus muscle.

6. Identify the boundaries of the popliteal fossa. These are:

(a)semitendinosus and semimembranosus above and medially;

(b) biceps femoris above and laterally;

(c) medial head of the gastrocnemius muscle below and medially; and

(d) lateral head of the gastrocnemius supplemented by the plantaris muscle below and laterally.

7. Study the origins of the calf muscles. Note that the lateral head of the gastrocnemius arises from the lateral surface of the lateral condyle of the femur while the medial head arises from the popliteal surface of the femur just above the medial condyle. The plantaris arises from the popliteal surface of the femur just above the lateral condyle of the femur.

8. Clean the contents of the popliteal fossa. Trace the termination of the small saphenous vein into the popliteal vein. Identify the division of the sciatic nerve into the tibial and common fibular nerves in the upper part of the fossa. Both branches give off genicular and muscular branches.

9. Note that the common fibular nerve runs along the medial margin of the biceps tendon.

10. Proceed to clean the popliteal vessels, the continuation of the femoral vessels. Note that the vein lies deep to the tibial nerve. Identify the artery which lies deep to the vein directly on the popliteal surface of the femur. Note the presence of popliteal lymph nodes in relation to the popliteal vessels (these are deep lymph nodes).

1. Note that the popliteal artery gives off genicular branches that accompany the corresponding genicular nerves.

2. Detach the two heads of the gastrocnemius muscle and the plantaris muscle from their origins.

3. Study the attachments of the popliteus. Note that it is attached proximally by a short rounded tendon to the anterior part of the popliteal groove on the lateral femoral condyle (it is also attached to the posterior cruciate ligament and the posterior part of the lateral meniscus, see later). The popliteus tendon which lies within the capsule of the knee joint issues out of the capsule to gain attachment below to the posterior surface of the tibia above the soleal line.

4. Identify the large soleus muscle lying deep to the gastrocnemius. It arises from the upper part of the posterior surface of the fibula and the soleal line of the tibia.

5. Find the combined tendons of the gastrocnemius, soleus and plantaris below forming the calcaneal tendon, which is inserted into the posterior aspect of the calcaneus.

6. Separate the soleus from the fibula and tibia and from the fibrous arcade covering the posterior tibial vessels and nerve. You can now see the transverse intermuscular septum of the leg covering the deep layer of calf muscles.

7. Trace the popliteal artery downwards and identify its terminal branches, the anterior and posterior tibial arteries, at the lower border of the popliteus muscle.

8. Observe the neurovascular bundle lying between the superficial flexors which have been reflected and the deep group. The tibial nerve gives muscular branches to the gastrocnemius, soleus, and the deep flexors. Clean these muscles and note the origin of:

(a)the flexor digitorum longus from the tibia;

(b) the flexor hallucis longus from the fibula; and somewhat deeper

(c) the tibialis posterior from both bones and the intervening interosseous membrane. 1

9. Follow the posterior tibial artery downwards and secure its most important branch the fibular artery which runs downwards and laterally deep to the flexor hallucis longus to supply the fibular muscles and the fibula. 20. Turn your attention to the region of the flexor retinaculum and identify the following structures lying deep to this retinaculum. From medial to lateral these are:

(a)tendon of tibialis posterior;

(b) tendon of flexor digitorum longus;

(c) posterior tibial vessels;

(d) tibial nerve; and

(e) flexor hallucis longus tendon. Note that the tendon of the flexor digitorum longus crosses the tendon of the tibialis posterior a short distance above the ankle.

Summary

The hip joint exhibits both stability and mobility. The stability of the joint can be gauged by:

(a)the congruence of the articular surfaces lined by articular cartilage;

(b) the depth of the acetabular cavity; and

(c) the strength of the muscles and ligaments. The role of the ligaments in the upright posture must be understood. This can be inferred from the fact that the centre of gravity of the trunk falls behind a line joining the centres of the femoral heads. Moreover, all the ligaments become increasingly taut during extension until the full congruence of the articular surfaces is brought about. This is the most stable or ‘locked’ position of the joint. The lig ament of the head of femur was originally a part of the fetal capsule, which has been pushed into the joint so that the synovial membrane tends to enclose it. In the child, the blood vessels passing through the ligamentum teres constitute the main source of blood supply to the head of the femur while in the adult, the branches of the profunda femoris take over this function. What will be the effect of a fracture of the neck of the femur in a child and in an adult? The popliteal fossa is a diamond shaped hollow behind the knee where the main vessels and nerves passing from the anterior and posterior aspects of the thigh come together and are subsequently re-arranged and distributed to the leg and foot. The sciatic nerve divides in the upper part of the popliteal fossa into its two functional components, the common fibular and tibial nerves. The common fibular nerve supplies the anterior (extensor) and lateral (fibular) compartments as well as the dorsum of the foot. The tibial nerve supplies the posterior compartment of the leg and the muscles of the sole of the foot. The popliteal artery, a continuation of the femoral artery at the opening in the adductor magnus, divides into anterior and posterior tibial arteries at the lower border of the popliteus. The anterior tibial artery after passing through the interosseous membrane supplies the anterior compartment of the leg and the dorsum of the foot. The posterior tibial artery supplies the back of the leg and sole of the foot while the fibular artery, a branch of the posterior tibial artery, supplies branches to the fibular compartment. The muscles of the back of the leg can be divided into a superficial group comprising the gastrocnemius, plantaris and soleus, and a deep group consisting of the flexor digitorum longus, flexor hallucis longus and tibialis posterior. These muscles are plantar flexors, in addition tibialis posterior is also an invertor. The superficial and deep groups are separated by a transverse intermuscular septum and the neurovascular plane lies between these two groups of muscles.