THE SKELETON OF THE FREE LOWER LIMB
The skeleton of the lower limb consists of the femur, or thigh bone, two leg bones, and the bones of the foot. Besides, a small (sesamoid) bone, the patella, adjoins the thigh bone.
The Femur
The femur, or thigh bone, is the largest and thickest long tubular bone. Like all such bones it is a long lever of movement and has a diaphysis, metaphyses, epiphyses, and apophyses in accordance with its development. The upper (proximal) end of the femur carries a spherical articular head (caput femoris) (epiphysis); a little downward from the centre of the head is a small rough depression (jovea capitis femoris), where the ligament of the head is attached. The head is connected with the rest of the bone by a neck (collum femoris) (metaphysis), which meets the axis of the femoral shaft at an obtuse angle (about 130 degrees); in the wider female pelvis this angle is closer to 90 degrees. Two bony prominences called trochanters (apophyses) are found at the junction of the neck with the shaft of the femur. The greater trochanter (trochanter major) is the upper end of the femoral shaft. On its medial surface, facing the neck, is the trochanteric fossa (fossa trochanterica). The lesser trochanter (trochanter minor) is at the inferior margin of the neck on the medial surface and a little to the back. Both trochanters are joined on the posterior surface of the femur by an oblique intertrochanteric crest (crista intertrochanterica) and on the anterior surface by the intertrochanteric line (linea intertrochanterica). All these structures, the trochanters, crest, line, and fossa, developed as a result of the attachment of muscles. The body (shaft) of the femur is slightly convex forward and has a rounded trihedral shape; its anterior and lateral surfaces are smooth, while the posterior surface bears a mark of attachment of the thigh muscles, linea aspera (a rough line) which has two lips: lateral (labium laterale) and medial (labium mediate). Both lips bear marks of muscle attachment in their proximal part: tuberositas glutea on the lateral lip for attachment of the gluteus maximus muscle and linea pectinea on the medial lip for attachment of the pectineus muscle. Below the lips diverge and enclose a smooth triangular popliteal surface (faciespoplitea) on the posterior surface of the femur. The lower (distal) thickened end of the femur forms two rounded, posteriorly turned medial and lateral condyles (condylus medialis and condylus lateralis) (epiphysis); the medial condyle protrudes downward more than the lateral. Despite the difference in the size of these two condyles, however, they are located on the same level because the femur in its natural position stands obliquely with its lower end closer to the midline than the upper end. Anteriorly the articular surfaces of the condyles blend with each other to form a small concavity in the sagittal direction. This common part of the articular surfaces is called facies patellaris because the posterior surface of the patella abuts against it in extension at the knee joint. On the posterior and inferior surfaces, the condyles are separated by a deep intercondylar fossa, or notch (fossa intercondylar is). Rough prominences are found on the sides of each condyle above the articular surface. These are the medial and lateral epicondyles (epicondylus medialis and epicondylus lateralis) (apophyses). Ossification. Radiographs of the proximal end of the femur at birth demonstrate only the diaphysis because the epiphysis, metaphysis, and apophyses (greater and lesser trochanters) are still in the cartilaginous developmental stage. The X-ray picture of the later changes is determined by the appearance of ossification nuclei in the femoral head (epiphysis) at the age of one, in the greater trochanter (apophysis) between the ages of three and four, and in the lesser trochanter between the ages of 9 and 14. Fusion occurs in the reverse order between the ages of 17 and 19.
The Patella
The patella, or knee-cap, is none other than a large sesamoid bone lodged in the tendon of the quadriceps femoris muscle stretching over the anterior surface of the knee joint. A superior wide end, the base (basispatellae), and a pointed inferior end or apex (apex patellae) are distinguished. The anterior surface of the patella is rough, while the posterior surface has smooth articular surface (facies articularis) by which the patella comes into contact with the patellar surface of the femur described above.
The Hip Joint
The hip joint (art. coxae) is formed by the cup-like acetabulum of the hip bone, by its facies lunata to be more precise, and the femoral head fitting into it (Fig. 100). A fibrocartilaginous ring (labrum acetabulare) is attached to the whole rim of the acetabulum and makes the cavity deeper so that its depth is more that half a spheroid. The fibrocartilaginous rim bridges the acetabular notch and forms the transverse ligament of the acetabulum (lig. transversum acetabuli). The acetabulum is covered with hyaline articular cartilage only in the area of the lunate surface, while the acetabular fossa is filled with loose fatty tissue and the base of the ligament of the femoral head. The surface of the femoral head articulating with the acetabulum forms in general two-thirds of a spheroid. It is covered with hyaline cartilage with the exception of the fovea capitis giving attachment to the ligament of the head. The articular capsule of the hip joint is attached along the whole rim of the acetabulum. In the region of the acetabular notch it fuses with the transverse ligament of the acetabulum, leaving a free opening between this ligament and the edges of the notch. Air-tightness of the joint here is provided by the synovial membrane covering the ligament of the head. The articular capsule is attached to the femur in front along the entire distance of the intertrochanteric line and behind to the femoral neck parallel to and medial of the intertrochanteric crest. As a result of such a line of attachment of the capsule on the femur, most of the neck is enclosed in the cavity of the joint. The hip joint has two other intra-articular ligaments, the above-mentioned transverse ligament of the acetabulum and the ligament of the head (lig. capitis femoris) whose base is attached to the edges of the acetabular notch and to the transverse ligament of the acetabulum. The apex is attached to the fovea capitis femoris. The ligament of the head is covered by a synovial sheath rising over it from the floor of the acetabulum. It is an elastic padding which absorbs the shocks experienced by the joint and transmits the vessels to the femoral head. That is why the head does not necrotize in fractures of the femoral neck if the synovial sheath remains intact, and vice versa. The hip joint is a ball-and-socket joint of the limited type (cotyloid joint) and therefore permits movement, though not as freely as a free ball-and-socket joint, on three main axes: frontal, sagittal, and vertical. Circumduction is also possible. Flexion (to the front) and extension (to the back) of the lower limb occur on the frontal axis. The freest of these two movements is forward flexion because there is no tension of the fibrous capsule, which has no attachment to the femoral neck at the back. Flexion is greatest (118-121 degrees) when the knee is bent so that the thigh can be brought against the anterior abdominal wall; when the knee is in extension, flexion of the limb is limited (84-87 degrees) by tension of the muscles on the posterior surface of the thigh; when the knee is bent these muscles are relaxed. Extension of a flexed limb is possible to a vertical position. Further movement to the back (posterior flexion) is greatly limited (to about 19 degrees) by tension of the iliofemoral ligament: if, despite this, we extend the limb still further, this is accomplished through movement at the contralateral hip joint. Movement about the sagittal axis consists in abduction of the limb (or limbs when they are drawn apart at the same time laterally) and in adduction when the limb moves to the midline. Abduction is possible to 70-75 degrees. Medial and lateral rotation of the limb on the vertical axis has a range of 90 degrees. The external ligaments of the joint are arranged in accordance with the three main pivotal axes: three longitudinal ligaments (ligamenta iliofemorale, pubofemoral and ischiofemorale), which pass perpendicular to the horizontal axes (frontal and sagittal), and one circular (zona orbicularis), which is perpendicular to the vertical axis. The iliofemoral (Bertin's) ligament (lig. iliofemorale) is on the anterior aspect of the joint. Its apex is attached to the anterior inferior iliac spine and its widened base to the trochanteric line. It resists extension and prevents the body from falling backward when walking erect. This explains the high development of Bertin's ligament in man. It is the strongest ligament in the human body and can withstand a load of 300 kg. The pubofemoral ligament (lig. pubofemorale) is on the infero-medial aspect of the joint; it stretches from the pubis to the lesser trochanter and blends with the capsule. It resists abduction and checks lateral rotation. The ischiofemoral ligament (lig. ischiofemorale) begins on the posterior aspect of the joint at the acetabular rim in the region of the ischium, passes laterally and upward over the femoral neck, blends with the capsule, and attaches to the anterior edge of the greater trochanter. It limits medial rotation of the thigh and together with the lateral part of Bertin's ligament resists adduction. 4. The orbicular zone (zona orbicularis) consists of circular fibres in the deep layers of the articular capsule under the longitudinal ligaments described above (see Fig. 100). These fibres embrace the femoral neck like a loop and attach above to the bone under the anterior inferior iliac spine. The circular arrangement of the orbicular zone corresponds to the rotational movements of the thigh. In a living person the ligaments do not stretch maximally because movements are checked to a certain degree by the tension of the muscles around the joint. All the described movements of the lower limb at the hip joint may take place when the limb is relieved of the weight of the body, as occu rs, for example, when a person is standing on the other limb. Forward and backward flexion of the limb also occurs in walking or running, when the body is supported by alternating limbs, while the limb that is freed of the weight makes a forward motion. When the lower limbs are fastened, i.e. stand fast in one spot, movement of the hip bone at the hip joint may take place only with movement of the whole upper part of the body, as it occurs, for instance, when a person bends the body in a bow and unbends it while the limbs rest on the ground. The same happens when a person rises from a supine position: the lower limbs lie on a plane, while the pelvis with the trunk rises and moves at the hip joints. The great number of ligaments and the more pronounced curvature and congruence of the articulating surfaces of the hip joint, as compared to the shoulder joint, make movements at the hip joint less free than those at the shoulder. This is linked with the function of the lower limb, which requires greater stability in this joint. Because of this limitation and the strength of the hip joint, dislocations there are rarer than in the shoulder joint. Radiographs of the hip joint (Fig. 101) made at different views produce detailed images of the pelvic bones and femur simultaneously. The floor and roof are distinguished in the acetabulum roentgenological-ly. The floor is bounded medially by a funnel-shaped area of diminished density ("star figure") corresponding to the anterior part of the body of the ischium. The roof (upper border of the acetabulum) is normally round but sharpens in pathological cases. The articular, femoral, head has a spherical shape and even contours on the radiograph, with the exception of the fovea capitis femoris which produces a depression with irregular contours; the latter must not be mistaken for a focus of bone destruction. An "X-ray joint space"1 is seen between the femoral head sunken into the acetabulum and the roof of the acetabulum. The normal relations between the articular head and the acetabulum are characterized by the sinking of the head into the acetabulum and by Nelaton's line drawn from the medial contour of the femoral head to the upper border of the obturator foramen. It is arched normally but broken in subluxation. In judging sex, age, and constitutional features, it is important to take into consideration the angle formed by the femoral neck and the diaphysis. In a living person this angle can be determined only by X-ray. It ranges between 130 and 135 degrees in adult males. It is larger in children and smaller in old people, and it is smaller in females than in males. The hip joint is supplied with arterial blood from the rete articulare formed by branches of the medial and lateral circumflex femoral arteries (from the deep femoral artery) and the obturator artery. The latter gives origin to the acetabular branch, which passes through the ligament of the head of the femur to the femoral head. Venous blood drains into the deep veins of the thigh and pelvis, the deep femoral, femoral, and internal iliac veins. Lymph drains along the deep lymphatics into the deep inguinal lymph nodes. The articular capsule is innervated by the obturator, femoral, and sciatic nerves.
The Femur
The femur, or thigh bone, is the largest and thickest long tubular bone. Like all such bones it is a long lever of movement and has a diaphysis, metaphyses, epiphyses, and apophyses in accordance with its development. The upper (proximal) end of the femur carries a spherical articular head (caput femoris) (epiphysis); a little downward from the centre of the head is a small rough depression (jovea capitis femoris), where the ligament of the head is attached. The head is connected with the rest of the bone by a neck (collum femoris) (metaphysis), which meets the axis of the femoral shaft at an obtuse angle (about 130 degrees); in the wider female pelvis this angle is closer to 90 degrees. Two bony prominences called trochanters (apophyses) are found at the junction of the neck with the shaft of the femur. The greater trochanter (trochanter major) is the upper end of the femoral shaft. On its medial surface, facing the neck, is the trochanteric fossa (fossa trochanterica). The lesser trochanter (trochanter minor) is at the inferior margin of the neck on the medial surface and a little to the back. Both trochanters are joined on the posterior surface of the femur by an oblique intertrochanteric crest (crista intertrochanterica) and on the anterior surface by the intertrochanteric line (linea intertrochanterica). All these structures, the trochanters, crest, line, and fossa, developed as a result of the attachment of muscles. The body (shaft) of the femur is slightly convex forward and has a rounded trihedral shape; its anterior and lateral surfaces are smooth, while the posterior surface bears a mark of attachment of the thigh muscles, linea aspera (a rough line) which has two lips: lateral (labium laterale) and medial (labium mediate). Both lips bear marks of muscle attachment in their proximal part: tuberositas glutea on the lateral lip for attachment of the gluteus maximus muscle and linea pectinea on the medial lip for attachment of the pectineus muscle. Below the lips diverge and enclose a smooth triangular popliteal surface (faciespoplitea) on the posterior surface of the femur. The lower (distal) thickened end of the femur forms two rounded, posteriorly turned medial and lateral condyles (condylus medialis and condylus lateralis) (epiphysis); the medial condyle protrudes downward more than the lateral. Despite the difference in the size of these two condyles, however, they are located on the same level because the femur in its natural position stands obliquely with its lower end closer to the midline than the upper end. Anteriorly the articular surfaces of the condyles blend with each other to form a small concavity in the sagittal direction. This common part of the articular surfaces is called facies patellaris because the posterior surface of the patella abuts against it in extension at the knee joint. On the posterior and inferior surfaces, the condyles are separated by a deep intercondylar fossa, or notch (fossa intercondylar is). Rough prominences are found on the sides of each condyle above the articular surface. These are the medial and lateral epicondyles (epicondylus medialis and epicondylus lateralis) (apophyses). Ossification. Radiographs of the proximal end of the femur at birth demonstrate only the diaphysis because the epiphysis, metaphysis, and apophyses (greater and lesser trochanters) are still in the cartilaginous developmental stage. The X-ray picture of the later changes is determined by the appearance of ossification nuclei in the femoral head (epiphysis) at the age of one, in the greater trochanter (apophysis) between the ages of three and four, and in the lesser trochanter between the ages of 9 and 14. Fusion occurs in the reverse order between the ages of 17 and 19.
The Patella
The patella, or knee-cap, is none other than a large sesamoid bone lodged in the tendon of the quadriceps femoris muscle stretching over the anterior surface of the knee joint. A superior wide end, the base (basispatellae), and a pointed inferior end or apex (apex patellae) are distinguished. The anterior surface of the patella is rough, while the posterior surface has smooth articular surface (facies articularis) by which the patella comes into contact with the patellar surface of the femur described above.
The Hip Joint
The hip joint (art. coxae) is formed by the cup-like acetabulum of the hip bone, by its facies lunata to be more precise, and the femoral head fitting into it (Fig. 100). A fibrocartilaginous ring (labrum acetabulare) is attached to the whole rim of the acetabulum and makes the cavity deeper so that its depth is more that half a spheroid. The fibrocartilaginous rim bridges the acetabular notch and forms the transverse ligament of the acetabulum (lig. transversum acetabuli). The acetabulum is covered with hyaline articular cartilage only in the area of the lunate surface, while the acetabular fossa is filled with loose fatty tissue and the base of the ligament of the femoral head. The surface of the femoral head articulating with the acetabulum forms in general two-thirds of a spheroid. It is covered with hyaline cartilage with the exception of the fovea capitis giving attachment to the ligament of the head. The articular capsule of the hip joint is attached along the whole rim of the acetabulum. In the region of the acetabular notch it fuses with the transverse ligament of the acetabulum, leaving a free opening between this ligament and the edges of the notch. Air-tightness of the joint here is provided by the synovial membrane covering the ligament of the head. The articular capsule is attached to the femur in front along the entire distance of the intertrochanteric line and behind to the femoral neck parallel to and medial of the intertrochanteric crest. As a result of such a line of attachment of the capsule on the femur, most of the neck is enclosed in the cavity of the joint. The hip joint has two other intra-articular ligaments, the above-mentioned transverse ligament of the acetabulum and the ligament of the head (lig. capitis femoris) whose base is attached to the edges of the acetabular notch and to the transverse ligament of the acetabulum. The apex is attached to the fovea capitis femoris. The ligament of the head is covered by a synovial sheath rising over it from the floor of the acetabulum. It is an elastic padding which absorbs the shocks experienced by the joint and transmits the vessels to the femoral head. That is why the head does not necrotize in fractures of the femoral neck if the synovial sheath remains intact, and vice versa. The hip joint is a ball-and-socket joint of the limited type (cotyloid joint) and therefore permits movement, though not as freely as a free ball-and-socket joint, on three main axes: frontal, sagittal, and vertical. Circumduction is also possible. Flexion (to the front) and extension (to the back) of the lower limb occur on the frontal axis. The freest of these two movements is forward flexion because there is no tension of the fibrous capsule, which has no attachment to the femoral neck at the back. Flexion is greatest (118-121 degrees) when the knee is bent so that the thigh can be brought against the anterior abdominal wall; when the knee is in extension, flexion of the limb is limited (84-87 degrees) by tension of the muscles on the posterior surface of the thigh; when the knee is bent these muscles are relaxed. Extension of a flexed limb is possible to a vertical position. Further movement to the back (posterior flexion) is greatly limited (to about 19 degrees) by tension of the iliofemoral ligament: if, despite this, we extend the limb still further, this is accomplished through movement at the contralateral hip joint. Movement about the sagittal axis consists in abduction of the limb (or limbs when they are drawn apart at the same time laterally) and in adduction when the limb moves to the midline. Abduction is possible to 70-75 degrees. Medial and lateral rotation of the limb on the vertical axis has a range of 90 degrees. The external ligaments of the joint are arranged in accordance with the three main pivotal axes: three longitudinal ligaments (ligamenta iliofemorale, pubofemoral and ischiofemorale), which pass perpendicular to the horizontal axes (frontal and sagittal), and one circular (zona orbicularis), which is perpendicular to the vertical axis. The iliofemoral (Bertin's) ligament (lig. iliofemorale) is on the anterior aspect of the joint. Its apex is attached to the anterior inferior iliac spine and its widened base to the trochanteric line. It resists extension and prevents the body from falling backward when walking erect. This explains the high development of Bertin's ligament in man. It is the strongest ligament in the human body and can withstand a load of 300 kg. The pubofemoral ligament (lig. pubofemorale) is on the infero-medial aspect of the joint; it stretches from the pubis to the lesser trochanter and blends with the capsule. It resists abduction and checks lateral rotation. The ischiofemoral ligament (lig. ischiofemorale) begins on the posterior aspect of the joint at the acetabular rim in the region of the ischium, passes laterally and upward over the femoral neck, blends with the capsule, and attaches to the anterior edge of the greater trochanter. It limits medial rotation of the thigh and together with the lateral part of Bertin's ligament resists adduction. 4. The orbicular zone (zona orbicularis) consists of circular fibres in the deep layers of the articular capsule under the longitudinal ligaments described above (see Fig. 100). These fibres embrace the femoral neck like a loop and attach above to the bone under the anterior inferior iliac spine. The circular arrangement of the orbicular zone corresponds to the rotational movements of the thigh. In a living person the ligaments do not stretch maximally because movements are checked to a certain degree by the tension of the muscles around the joint. All the described movements of the lower limb at the hip joint may take place when the limb is relieved of the weight of the body, as occu rs, for example, when a person is standing on the other limb. Forward and backward flexion of the limb also occurs in walking or running, when the body is supported by alternating limbs, while the limb that is freed of the weight makes a forward motion. When the lower limbs are fastened, i.e. stand fast in one spot, movement of the hip bone at the hip joint may take place only with movement of the whole upper part of the body, as it occurs, for instance, when a person bends the body in a bow and unbends it while the limbs rest on the ground. The same happens when a person rises from a supine position: the lower limbs lie on a plane, while the pelvis with the trunk rises and moves at the hip joints. The great number of ligaments and the more pronounced curvature and congruence of the articulating surfaces of the hip joint, as compared to the shoulder joint, make movements at the hip joint less free than those at the shoulder. This is linked with the function of the lower limb, which requires greater stability in this joint. Because of this limitation and the strength of the hip joint, dislocations there are rarer than in the shoulder joint. Radiographs of the hip joint (Fig. 101) made at different views produce detailed images of the pelvic bones and femur simultaneously. The floor and roof are distinguished in the acetabulum roentgenological-ly. The floor is bounded medially by a funnel-shaped area of diminished density ("star figure") corresponding to the anterior part of the body of the ischium. The roof (upper border of the acetabulum) is normally round but sharpens in pathological cases. The articular, femoral, head has a spherical shape and even contours on the radiograph, with the exception of the fovea capitis femoris which produces a depression with irregular contours; the latter must not be mistaken for a focus of bone destruction. An "X-ray joint space"1 is seen between the femoral head sunken into the acetabulum and the roof of the acetabulum. The normal relations between the articular head and the acetabulum are characterized by the sinking of the head into the acetabulum and by Nelaton's line drawn from the medial contour of the femoral head to the upper border of the obturator foramen. It is arched normally but broken in subluxation. In judging sex, age, and constitutional features, it is important to take into consideration the angle formed by the femoral neck and the diaphysis. In a living person this angle can be determined only by X-ray. It ranges between 130 and 135 degrees in adult males. It is larger in children and smaller in old people, and it is smaller in females than in males. The hip joint is supplied with arterial blood from the rete articulare formed by branches of the medial and lateral circumflex femoral arteries (from the deep femoral artery) and the obturator artery. The latter gives origin to the acetabular branch, which passes through the ligament of the head of the femur to the femoral head. Venous blood drains into the deep veins of the thigh and pelvis, the deep femoral, femoral, and internal iliac veins. Lymph drains along the deep lymphatics into the deep inguinal lymph nodes. The articular capsule is innervated by the obturator, femoral, and sciatic nerves.