BIOLOGY 03048, ANATOMY WEEK 13: LOWER EXTREMITY ISSUES 11/23/99
W. Crone (303 FTZ, 629-7439, cronewil@hvcc.edu, http://www.hvcc.edu/academ/faculty/crone/index.html)
Moore and Dalley: Ch. 5
possible web sites: http://www.med.und.nodak.edu/depts/fpc/knee3/knee-1.htm (knee injury case study)
http://www.scoi.com (multiple brief summaries of orthopedic conditions and operations)
Knee extensors:
The rectus femoris muscle arises from the anterior inferior iliac spine. Since it is the only one of the quadriceps to cross the hip, it can flex the hip in addition to extending the knee (good for kicking a football). Three vasti round out the quadriceps: vastus medialis, vastus lateralis, and vastus intermedius mm. They all insert into the tibial tuberosity via the quadriceps tendon, the patella (a big sesamoid bone), and the patellar ligament" ). Alterations in the Q angle between the above tendon/ligament lead to imbalanced quads as in"runner's knee" (chondromalacia patellae or patellofemoral syndrome) with vastus medialis weakness.1 Charley horse" or thigh stiffness, tenderness from direct trauma.3
Thigh adductors: (gracilis, pectineus, adductor longus, adductor brevis, and adductor magnus muscles). These four arise off of pubis and insert on aspects of the linea aspera."Groin pulls" when adductors/flexors are injured, especially adductor longus muscle.1
Knee flexors: the hamstrings (semimembranosus, semitendinosus, and biceps femoris muscles). Their main set of action is to flex the knee and extend the thigh. The tendons of insertion can be easily seen forming the depression behind the knee known as the popliteal fossa."Hamstring pulls" when these are injured, particularly with quick-start sports.3
BLOOD SUPPLY:
The external iliac artery under the inguinal ligament and becomes the femoral artery. It enters the thigh from the midline anteriorly along the medial intermuscular septum. The profunda femoris (deep femoral) artery off of the femoral a. supplies the back side of the thigh. Anteriorly, the femoral artery is covered by sartorius in a fascial space known as the adductor canal. In there, the femoral artery descends toward the knee. The femoral artery sneaks through an opening in adductor magnus, the adductor hiatus, to reach the muscles behind the knee and become the popliteal artery.
The femoral triangle is formed by the inguinal ligament, the sartorius, and the adductor longus. In here are the femoral nerve, artery, vein, empty space, and lymphatics (NAVEL). The femoral triangle has clinical significance for the availability of a femoral pulse, for femoral vessel access for catheterization, and for femoral hernias through the femoral ring of the femoral canal around the empty space and lymphatics.3
Superficial vs. deep veins: the small (short) saphenous vein runs up posterolaterally to knee level, where it turns deep into the popliteal region to join the popliteal vein. Anterior to the medial malleolus, the great (long) saphenous vein courses up the entire length of the limb. Its valves can break down, leading to varicosities. The great saphenous vein runs in the subcutaneous fat until it pierces the saphenous opening of the fascia lata to reach the femoral vein. Deep veins of the lower limb correspond to arteries. Thrombophlebitis, particularly of the deep veins, can send dangerous clots or emboli through to the pulmonary arteries, leading to pulmonary thromboembolism.2,4,5 Finally, the lympatic vessels of the lower limb drain into inguinal lymph nodes, as do the perineal and gluteal regions.
LONG BONES: Distal femur with two articular condyles, with a superior articular surface for the patella. Lateral/medial epicondyles for attachment of the collateral ligaments of the knee. The anterior tibial tuberosity as the insertion for the knee extensor ligament (patellar ligament). At the distal end of the tibia, a medial malleolus that supports the ankle joint medially and is a pulley for several tendons. The fibula terminates in a lateral malleolus.
THE KNEE JOINT: The knee joint involves articulations among three bones: femur, tibia, and patella. A hinge joint, the knee shows flexion, extension, sometimes hyperextension (e.g., swimming), and some rotation (e.g., popliteus m.). Upon the tibial plateau, the lateral meniscus (semilunar cartilage) is flatter than the more cupped medial meniscus, which serves the purpose of deepening of the socket for the medial femoral condyle. The tight hold on the medial meniscus leads to its higher rate of tears.
The anterior cruciate ligament prohibits backward dislocation of the femur. The stronger posterior cruciate ligament prevents forward dislocation of the femur. To prevent lateral or medial displacement, collateral ligaments are present. These become fully taut upon knee extension. Unhappy triad (of O'Donoghue): rupture of medial (tibial) collateral ligament, tear of ACL, and medial meniscus damage, as with a valgus stress.2,3 The patella or kneecap: bones developed in a tendon are called sesamoid bones. The patella helps to increase the leverage of the knee extensors. Patellar reflex tests (L2, L3) L4.
The synovial membrane generally follows the attachment of the three bones (femur, tibia, and patella), but has a laxness built in to allow flexion. The synovial membrane rises posterior to and above the patella as the suprapatellar bursa (thus allowing for joint effects to be visible there and vice-versa, e.g., effusion).
BONES OF THE FOOT: Looking at a foot outline, the anterior half are the long bones of metatarsals and phalanges (stress fractures for metatarsals if sudden overuse), and in the posterior half are the tarsal bones. The talus is the basis for the ankle joint, and the calcaneus is the heel bone. The talus is set at a slight angle to the calcaneus. The posterior calcaneal tuberosity is a lever for the calf muscles. The navicular, cuboid, and three cuneiforms make up the other tarsal bones, giving flexibility to the foot (inversion and eversion are tarsal movements).
THE ANKLE JOINT: In order to add security to the ankle joint, the tibia and fibula are joined in several ways, e.g., with ligaments near the malleoli, and an interosseus membrane joins the shafts of the tibia and fibula. The role of the ankle joint is that of a weight-bearing hinge joint, with dorsiflexion and plantarflexion. The inferior end of the tibia is concave and sits over the talus. The talus is flanked by bony flanges, the medial and lateral malleoli. As with other hinge joints, the capsule of the ankle joint are thickened to form collateral ligaments. Laterally, a calcaneofibular ligament reaches to the calcaneus. More anteriorly, a weak anterior talofibular ligament from the front of the lateral malleolus to the neck of the talus. The ankle joint is the most frequently injured of the major articulations in the body via inversion ankle sprains. The lateral ligaments just mentioned take the brunt in such an incident. Medially, the deltoid (medial) ligament of the ankle would be affected in eversion sprains, but is very strong.
MUSCLES OF THE LEG: One can think of the leg muscles in three major groups, depending on where tendons cross the ankle joint, as well as their position.
A. anterior compartment extensors with tendons in front of the ankle
B. lateral compartment peronei with tendons behind the lateral malleolus
C. posterior compartment flexors with tendons behind the ankle
A. extensors (dorsiflexors) are lateral to the tibia, anterior to the fibula. Their innervation is the deep peroneal (fibular) nerve (deep branch of the common peroneal (fibular) nerve).
1) tibialis anterior m., most important, powerful, and medial of the dorsiflexors. It dorsiflexes the ankle, and inverts the foot. It prevents toe-stubbing and so when paralyzed can lead to foot-drop, e.g, from damage to the common peroneal (fibular) nerve in its superficial position as it winds around the neck of the fibula. Also, anterior compartment syndrome: muscle expansion with pain and tenderness in anterolateral aspect of leg, with the potential for necrosis and loss of dorsiflexion if not treated promptly. In contrast, the term shin splints (medial tibial stress syndrome) represents a less serious collection of subclinical periosteal or mild muscle inflammation.1,2
2) extensor digitorum longus m., to the dorsal surface of the phalanges of 2nd through 5th toes.
3) extensor hallucis longus m.: a special extensor for the hallux (big toe).
To hold the tendons of the extensors in place and not have them bowstringing, there are fibrous bands or retinacula
(-um, singular) around the ankle: superior and inferior extensor retinacula (retinacula exist for other muscles as well).
B. peroneal (fibular) muscles. The peroneus (fibularis) longus and the peroneus (fibularis) brevis mm. are in the lateral component. Both use the lateral malleolus as a pulley. The nerve supply for the peroneal muscles is the superficial peroneal (fibular) nerve, a branch of the common peroneal. The peroneal muscles evert (and plantarflex) the foot, which is helpful for maintaining footing over uneven surfaces.
C. plantarflexors. The gastrocnemius and soleus make up the calf of the foot, with an associated plantaris. The three muscles are supplied by branches of the tibial nerve.
1) The gastrocnemius m. has lateral and medial heads from origins from origins behind the two condyles. They unite to form a single muscle and then a wide and flat tendon.
2) The soleus m. has a large, flattened belly along the posterior surfaces of the tibia and fibula.
3) the plantaris m. has an origin off the lateral condyle of the femur, and can painfully rupture.3
All three share a common insertion tendon, the tendo calcaneus (Achilles tendon). These are are active in take-off (plantarflexing) phase of walking and running. Achilles tendinitis at musculotendinous junction with overuse, poor warmup.3 The ankle reflex tests S1.
The deep flexors ("Tom, Dick, an' Harry"), tibialis posterior m., flexor digitorum longus m., and flexor hallucis longus m. are"push off muscles" that can be involved in a posterior compartment form of"shin splints."1
FOOT: Low lateral longitudinal arch and higher medial longitudinal arch, with main support of the central, thickened deep fascia of the sole (plantar aponeurosis) and plantar ligaments, e.g., the spring or calcaneonavicular ligament. Plantar fasciitis, inflammation of the plantar aponeurosis with tenderness at calcaneal origin. It is connected between the calcaneal tuberosity and the ligaments associated with the metatarsal heads. Flatfoot (pes planus) is a weakening of the arches leading to an eversion so that more of the sole contacts the ground. Hence therapy should include 1) transferring body weight to the lateral side of the foot (arch supports) and 2) strengthening invertors and plantarflexors to support the medial longitudinal arch under stress and during movement.2
BLOOD SUPPLY TO THE LEG AND FOOT: The posterior tibial artery is palpable behind medial malleolus, and anterior tibial artery as the dorsalis pedis artery is palpable on the dorsum of the foot, as ways for checking lower extremity circulation.
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