Lab 15 Pre-Lab Exercise:
The femur is the largest long bone in the body and the only bone in the thigh (as the humerus is the only bone in the arm). Proximally, it is marked by the large, globular femoral head, the femoral neck, and the greater trochanter. The femoral head articulates with the acetabulum of the innominate (note the smooth surface of the femoral head at this articulation).
The femoral shaft (diaphysis) is generally very robust with a slight anterior curvature. Dorsomedialy, the shaft is marked near its proximal end by the lesser trochanter. At its distal end, the femoral shaft expands into the lateral and medial femoral condyles. These condyles provide articulation with the proximal tibia, forming the knee joint. However the femur is not in direct line with the tibia; it angles medially from the acetabulum toward the knee (valgus knee). The articular surface of the condyes is expanded anteriorly to provide a groove for the patella (knee cap).
1. Examine a disarticulated femur. Locate the most important sites of muscle attachment to this bone:
- The greater trochanter (insertions of the deeper glutei and lateral rotator muscles)
- The lesser trochanter (insertion of the iliopsoas muscle)
- The linea aspera along the whole length of the posterior surface of the shaft (origin of the medial and lateral vasti muscles and the short head of the biceps femoris; insertion of the adductors muscles, pectineus, and gluteus maximus)
- Medial and lateral epicondyles (origin of the plantaris and gastrocnemius muscles)
- The adductor tubercle (insertion of the adductor magnus muscle - hamstring portion).
The patella (knee cap) is the largest sesamoid bone in the body. Sesamoid bones develop within tendons and often function to increase the leverage of the tendons in which they are imbedded. The patella resides within the quadriceps tendon and also helps stabilize the tendon during knee flexion. The patella does not develop until between two to six years of age.
1. Examine a disarticulated patella and identify the following:
- The flat and proximal base.
- The distally pointing apex.
- Two articular facets on the dorsal side of the patella: the smaller medial facet and the larger lateral facet that articulate with the medial and lateral femoral condyles, respectively.
3. The leg
The leg contains two bones. The tibia is the larger of the two and is in the medial part of the leg. The fibula is in the lateral part of the leg and is much thinner.
The tibia is generally triangular in cross-section, with one of the angles of the triangle forming the sharp surface of the shin. Proximally, the lateral and medial condyles articulate with their femoral counterparts. Distally, the tibia articulates with the talus at the ankle joint. The distal medial malleolus lies just medial to the tibio-talar articulation.
1. Examine a disarticulated tibia and identify the following:
- The proximal medial and lateral condyles of the tibial plateau.
- The proximal and anteior tibial tuberosity, the attachment site for the quadriceps tendon.
- The sharp and palpable anterior border.
- The lateral interoseous border.
- The distal medial malleolus.
- The distal articular surface for the talar trochlea.
The fibula is the smaller bone of the leg. It lies lateral to the tibia. Proximally, it articulates with the tibia at the superior tibiofibular articular surface. Distally, it articulates with the tibia and talus, and expands laterally to form the lateral malleolus.
1. Examine a disarticulated fibula and identify the following:
- The proximal fibular head.
- The medial interosseus border.
- The distal lateral malleolus.
4. Bony landmarks of the thigh and leg
Tendons, muscles and bony landmarks in the lower limb are used to locate major arteries, veins, and nerves. Because vessels are large, they can be used as entry points to the vascular system and in addition, the vessels in the lower limb are farthest from the heart and most inferior in the body. Therefore, the nature of peripheral pulses in the lower limb can give important information about the status of the circulatory system in general.
Femur: the femur articulates proximally with the innominate at the acetabulum and the tibia and patella at the knee. The greater trochanter is a hard bony protuberance that can be palpated laterally as you medially and laterally rotate and abduct the femur. It is about a hand’s width inferior to the midpoint of the iliac crest. The anterior surface of the femoral condyles can be palpated if the knee is fully flexed. The lateral and medial surfaces of the lateral and medial epicondyles respectively can be palpated when the knee is flexed. The adductor tubercle, which is found on the superior surface of the medial epicondyle, can also be palpated.
Patella: is a prominent feature and the entirety of it can be palpated. The tendon of the quadriceps femoris tendon attaches superiorly and the patellar ligament connects the inferior surface to the tibial tuberosity. Flex your knee and palpate the margins of the patella. Now extend your knee and move the patella from side to side and note that some of its posterior surface can be palpated as well.
Tibia: the medial and lateral tibial condyles can be palpated inferior to the femur and patella when the knee is flexed. The anterior border of the tibia is subcutaneous and can be palpated from the tibial tuberosity (proximal) to the medial malleolus (distal). The medial surface of the tibia is also subcutaneous and can be palpated for full length (inside leg). The medial malleolus is larger and more anterior and proximal than the lateral malleolus (fibula).
Fibula: the head of the fibula can be palpated as a protuberance on the lateral surface of the knee just inferior to the lateral condyle of the tibia and when the knee is flexed. It can also be located by following the tendon of the biceps femoris inferiorly (see below). The neck of the fibula is just inferior to the head of the fibula, and there lies the common fibular nerve, which is susceptible to damage at this point. It can often be felt as a cord like structure at this position. The lateral malleolus is smaller and extends further inferiorly and posteriorly than the medial malleolus.
5. Soft tissue of the thigh and leg
Sensation and muscle action in the lower limb are tested to assess lumbar and sacral regions of the spinal cord.
Sartorius: originates from the ASIS and crosses anteriorly over the thigh to attach to the medial aspect of the tibia below the knee joint. It can be palpated and seen when the hip joint is flexed, laterally rotated, and somewhat abducted and the knee joint is flexed.
Rectus femoris: can be felt centrally in the thigh descending to patella when the knee is extended against resistance.
Vastus lateralis: can be see lateral to the rectus femoris from just inferior to the greater trochanter to the patella.
Vastus medialis: can be seen in the lower third of the thigh medial to rectus femoris.
Patellar ligament: is found from the apex of the patella to the tibial tuberosity. A fat pad lies deep to it. A tap on the patellar ligament (tendon) tests the reflex activity mainly at spinal cord levels L3-L4.
Adductor longus: the tendon of this muscle can be palpated as a cord like structure that attaches to the bone immediately inferior to the pubic tubercle. Palpate the adductor longus when resisting adduction of the thigh.
Iliotibial tract: can be felt as a taunt band crossing the anterolateral aspect of the knee joint when the knee is fully extended. In this position, the anterior edge of the tract raises a sharp vertical fold of skin posterior to the lateral edge of the patella. A furrow is usually visible between it and the tendon of the quadriceps femoris just proximal to the patella.
Tendon of biceps femoris: can be felt distally to the head of the fibula when the knee joint is flexed against resistance.
Semitendinosus tendon and semimembranosus: palpate both of these structures as they form the medial boundary for the popliteal fossa.
Gastrocnemius: outline this muscle when standing on the tip of your toes.
Soleus: mainly covered by the gastrocnemius, but can protrude on either side of the gastrocnemius in the lower part of the calf.
6. Visualizing the contents of the femoral triangle
The femoral triangle is the depression formed in the anterior thigh between the medial margin of the adductor longus muscle, the medial margin of the sartorius muscle, and the inguinal ligament. The femoral artery descends into the thigh from the abdomen by passing under the inguinal ligament and into the femoral triangle. In the femoral triangle, its pulse is easily felt just inferior to the inguinal ligament midway between the pubic symphysis and the ASIS. Medial to the artery is the femoral vein and medial to the vein is the femoral canal, which contains lympahtics and lies immediately lateral to the pubic tubercle. The femoral nerve lies lateral to the femoral artery.
7. Visualizing the contents of the popliteal fossa
The popliteal fossa is a diamond-shaped depression formed between the hamstring and gastrocnemius muscle posterior to the knee. The medial and lateral heads of the gastrocnemius muscle forms the inferior margins of the diamond. Superior margins are formed laterally by the biceps femoris muscle and medially by the semitendinosus and semimembranosus muscles. The popliteal fossa contains the popliteal artery and vein, the tibial nerve, and the common fibular nerve. The popliteal artery is the deepest of the structures in the fossa and descends through the region from the upper medial side. As a consequence of its position, the popliteal artery pulse is difficult to find, but usually can be detected on deep palpation just medial to the midline of the fossa. The vein and nerves are found laterally to the femoral artery. The common fibular nerve curves laterally out of the popliteal fossa and crosses the neck of the fibula just inferior to the head. The small saphenous vein penetrates deep fascia in the upper part of the posterior leg and joins the popliteal vein.