Human Anatomy - Kotsan I. Ya. 2009

Skeleton of the Lower Limb
Articulations of the Bones of the Free Lower Limb

The BONES OF THE free lower limb are interconnected primarily by discontinuous joints—synovials joints (diarthrosis)—and continuous joints—synarthroses (ligaments, interosseous membranes).

The hip joint (articulatio coxae) connects the Pelvic Girdle to the free lower limb. It is formed by the HEAD of the Femur and the acetabulum of the hip bone (Fig. 78). On the part of the femur, the entire surface of the head participates in The formation of the joint, whereas on the part of the acetabulum, only the lunate surface does. To enlarge the articular surface on the pelvic bone, the lunate surface is supplemented by the acetabular labrum and the transverse acetabular ligament. The acetabular labrum (labrum acetabulare) is composed of fibrocartilage and attaches along the rim of the acetabulum. The transverse acetabular ligament (lig. transversum acetabuli) spans across the acetabular notch, bridging the lunate surface and the acetabular labrum.

The Joint Capsule of the hip joint attaches to the hip bone along the margin of the acetabulum in such a way that the acetabular labrum remains inside the joint cavity. On the femur, the joint capsule attaches anteriorly along the intertrochanteric line and posteriorly medial to the intertrochanteric crest, so that the greater part of the femoral neck is enclosed within the joint cavity. The hip joint capsule is exceptionally strong due to the ligaments woven into it.

The extracapsular ligaments of the hip joint include the following (Fig. 79):

— the iliofemoral ligament (lig. iliofemorale) originates from the anterior inferior iliac spine, runs along the anterior surface of the joint capsule, and attaches to the intertrochanteric line. This is the strongest ligament of the hip joint, capable of withstanding loads of up to 300 kg, with a thickness of about 1 cm. The iliofemoral ligament helps maintain an upright body posture and prevents excessive extension at the hip joint;

— the pubofemoral ligament (lig. pubofemorale) is triangular in shape. Its broad base originates from the superior ramus of the pubis and the body of the ilium near its junction with the pubic bone, while its narrow apex attaches to the medial segment of the intertrochanteric line. This ligament restricts thigh abduction;

— the ischiofemoral ligament (lig. ishiofemorale) is located on the posterior surface of the joint. It originates from the body of the ischium, runs almost horizontally lateralwards, and attaches near the trochanteric fossa of the greater trochanter. The ligament restricts medial Rotation of the thigh;

— the zona orbicularis is embedded within the thickness of the joint capsule, loops around the neck of the femur, and attaches to the ilium below the anterior inferior spine.

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Fig. 78. Hip joint (right, frontal section)

1 — epiphyseal line, 2 — articular Cartilage, 3 — hip (pelvic) bone, 4 — joint cavity, 5 — ligament of the head of femur, 6 — transverse acetabular ligament, 7 — joint capsule, 8 — ischial tuberosity, 9 — zona orbicularis, 10 — acetabular labrum

Fig. 79. Hip joint (right, anterior view)

1 — joint capsule, 2 — obturator canal, 3 — obturator membrane, 4 — pubofemoral ligament, 5 — iliofemoral ligament, 6 — anterior inferior iliac spine

Among the intracapsular ligaments of the hip joint, besides the aforementioned transverse acetabular ligament, is the ligament of the head of the femur (lig. capitis femoris), which originates from the transverse ligament and attaches to the fovea of the femoral head. This ligament plays a mechanical role in holding the femoral head within the acetabulum only during the Embryonic period. In adults, it does not participate in reinforcing the joint; instead, it serves as an elastic cushion for the femoral head and contains Blood Vessels that supply Nutrition to the proximal end of the femur.

The hip joint is simple and nut-like (spheroidal/ball-and-socket variety). Movements around three axes of rotation are possible within it. Flexion (forward movement of the thigh) and extension (backward movement of the thigh) occur around the frontal axis; abduction and adduction of the thigh relative to the midline occur around the sagittal axis; and lateral and medial rotation (supination and pronation) of the thigh occur around the vertical axis. In addition, circumduction (circular movement) is possible in the joint.

Thigh mobility in the hip joint is less than shoulder mobility in the shoulder joint because, firstly, the articular surfaces of the bones articulating in the hip joint are more congruent with each other; secondly, the Ligamentous apparatus of the hip joint is more developed; and thirdly, the hip joint is surrounded by significantly stronger Muscles.

Fig. 80. Knee joint (right, anterior view, joint capsule removed, Patella with the tendon of the quadriceps femoris Muscle pulled downwards)

1 — femur, 2 — posterior cruciate ligament, 3 — anterior cruciate ligament, 4 — medial meniscus, 5 — transverse ligament of the knee, 6 — tibial collateral ligament, 7 — deep infrapatellar bursa, 8 — patellar ligament, 9 — articular surface of patella, 10 — tendon of quadriceps femoris muscle, 11 — interosseous membrane of leg, 12 — Tibia, 13 — Fibula, 14 — anterior ligament of the head of fibula, 15 — fibular collateral ligament, 16 — lateral meniscus, 17 — lateral condyle, 18 — patellar surface

Fig. 81. Knee joint (right, posterior view)

1 — fibular collateral ligament, 2 — arcuate popliteal ligament, 3 — popliteus muscle (partially removed), 4 — interosseous membrane of leg, 5 — pes anserinus profundus, 6 — tibial collateral ligament, 7 — tendon of semimembranosus muscle, 8 — oblique popliteal ligament

The knee joint (articulatio genus) is the largest and most complex joint in The Human Body (Fig. 80, 81). This is due to the fact that it is precisely at this site that the longest levers of the lower limb (the femur and the bones of the leg) articulate, producing the greatest range of motion during locomotion.

The knee joint is formed by the articular surfaces of the condyles and the patellar surface of the distal end of the femur, the superior articular surface of the tibia, and the articular surface of the patella. It is a compound and incongruent joint. Inside the joint are two menisci—medial and lateral (meniscus medialis and meniscus lateralis)—which increase the congruence of the articular surfaces and also serve as elastic cushions that function as Shock absorbers during movements (walking, running, jumping, etc.). The menisci are crescent-shaped plates lying on the superior articular surface of the tibia. They are constructed of fibrocartilage. The thick outer margin of the meniscus is fused with the joint capsule, while the thin inner margin is free. The ends of the anterior and posterior horns of the menisci attach via short ligaments to the intercondylar eminence. Anteriorly, the lateral and medial menisci are connected to each other by the transverse ligament of the knee (lig. transversum genus).

The articular capsule of the knee joint attaches to the femur 1 cm proximal to the articular surfaces; on the tibia and patella, it runs directly along the margins of their articular surfaces. The joint capsule is thin, loose, and very spacious. Its inner surface is lined with a synovial membrane that covers the ligaments located within the joint cavity and forms numerous synovial villi and folds. The synovial villi increase the surface area for synovial fluid secretion. The synovial folds contain adipose tissue; extending into the joint cavity, they occupy part of the space that is otherwise roomy due to the incongruence of the articular surfaces. The most prominent among them are the paired alar folds (plicae alares), located inferiorly and on both sides of the patella, and the unpaired infrapatellar synovial fold (plica synovialis infrapatellaris), which is a downward continuation of the central part of the alar folds.

The knee joint is reinforced by intracapsular and extracapsular ligaments.

The intracapsular ligaments of the knee joint include the following:

— anterior cruciate ligament (lig. cruciatum anterius). It originates from the Medial surface of the lateral femoral condyle and attaches to the anterior intercondylar area of the tibia;

— posterior cruciate ligament (lig. cruciatum posterius). It originates from the inner surface of the medial femoral condyle, runs posteriorly and inferiorly, and attaches to the posterior intercondylar area of the tibia;

— anterior meniscofemoral ligament (lig. meniscofemorale anterius). It originates from the anterior horn of the medial meniscus, runs parallel to the anterior cruciate ligament, and attaches to the inner surface of the lateral femoral condyle;

— posterior meniscofemoral ligament (lig. meniscofemorale posterius). It originates from the posterior horn of the lateral meniscus, runs parallel to the posterior cruciate ligament, and attaches to the inner surface of the medial femoral condyle.

— transverse ligament of the knee (lig. transversum genus) connects the anterior horns of the lateral and medial menisci.

The extracapsular ligaments of the knee joint include the following:

— oblique popliteal ligament (lig. popliteum obliquum), which partially represents the terminal part of the semimembranosus tendon fibers. The fibrous fibers of this ligament originate from the medial condyle of the tibia, run superiorly and laterally along the posterior surface of the joint capsule, and, blending into the capsule, attach to the posterior surface of the femur proximal to its lateral condyle;

— arcuate popliteal ligament (lig. popliteum arcuatum). It originates on the posterior surface of the fibular head and the lateral epicondyle of the femur. The fibers of this ligament ascend, arch medially, partially attach to the oblique popliteal ligament, and then descend to attach to the posterior surface of the tibia;

— patellar ligament (lig. patellae), which is the continuation of the central fibers of the quadriceps femoris tendon. The ligament runs from the apex of the patella to the tibial tuberosity;

— medial patellar retinaculum (retinaculum patellae mediale), which is the continuation of the medial fibers of the quadriceps femoris tendon, formed by the tendon of the vastus medialis muscle. The ligament runs from the medial margin of the patella to the tibial tuberosity;

— lateral patellar retinaculum (retinaculum patellae laterale), which is the continuation of the lateral fibers of the quadriceps femoris tendon, formed by the tendon of the vastus lateralis muscle. The ligament runs from the lateral margin of the patella to the tibial tuberosity;

— fibular collateral ligament (lig. collaterale fibulare), which is a rounded fibrous cord about 5 mm thick, originating from the lateral epicondyle of the femur and attaching to the lateral surface of the fibular head. This ligament is separated from the joint capsule by a layer of loose Connective Tissue;

— tibial collateral ligament (lig. collaterale tibiale), which appears as a broad fibrous plate 10–12 mm wide, fused with the capsule and, through it, with the medial meniscus. The ligament originates from the medial epicondyle of the femur and attaches to the medial condyle of the tibia.

The knee joint possesses several synovial bursae (bursae synoviales) located between bones and muscle tendons at their attachment sites, or between other freely moving structures to reduce mutual friction. Some of these communicate with the joint cavity, significantly increasing its volume. The number and size of synovial bursae vary individually. The main ones are: the suprapatellar bursa (bursa suprapatellaris), located superior to the patella between the femur and the quadriceps tendon; the deep infrapatellar bursa (bursa infrapatellaris profunda), lying between the patellar ligament and the tibia; and the subpopliteal recess (recessus subpopliteus), situated beneath the tendon of the popliteus muscle. On the anterior surface of the knee joint lies the subcutaneous prepatellar bursa (bursa subcutanea prepatellaris), which allows the Skin to glide smoothly over the anterior surface of the patella.

The knee joint is compound and complex (due to the presence of menisci), and condylar in shape. In terms of its range of motion, it is a combination of a hinge (ginglymus) and pivot joint, classified as a trochoginglymus (or pivot-hinge) joint. Movements are possible around two axes: frontal and vertical. Flexion (backward movement of the leg) and extension (forward movement of the leg) occur around the frontal axis. Rotation of the leg around the vertical axis is only possible when the knee is semi-flexed (when fully extended, rotational movements are prevented by the taut joint ligaments).