Joints of the Lower Limb

Hip Joint

The hip joint is an articulation between the hemispherical head of the femur and the cup-shaped acetabulum of the hip bone.
The acetabular notch at the lower part of the acetabulum is bridged by the transverse ligament of the acetabulum.
To the rim of the acetabulum is firmly attached a fibrocartilaginous ring, the acetabular labrum which deepens the acetabulum and clasps the head of the femur to form a more stable joint.
The round ligament of the head of the femur is attached to the transverse acetabular ligament and extends to the fovea centralis on the head of the femur.

Examine the articular capsule of the hip joint from the front. First, note its attachment to the intertrochanteric line and to the bases of the greater and lesser trochanters.

Define the strongest of the ligaments of the capsule, the iliofemoral ligament. Note that its apex is attached to the ilium between the two heads of the rectus femoris muscle. Identify the two limbs of the ligament, one passing to the base of the grater trochanter and other to the base of the lesser trochanter. Observe, in the image above, just how thick this capsular ligament is.

Next observe the pubofemoral ligament on the inferomedial aspect of the capsule. Follow this ligament to its attachment to the base of the lesser trochanter and examine its wide attachment to the superior ramus of the pubis, just above the obturator foramen. You can see that this capsular ligament is somewhat thinner if you take a look at it cut in cross section in the image above.

If you examine the posterior aspect of the hip joint, you can define the fibers of the ischiofemoral ligament as they sweep over the neck of the femur.

The capsule of the hip joint is very loose as it covers the posterior aspect of the neck of the femur and does not cover the neck of the femur completely.

The hip joint receives its blood supply from small vessels which reach it by running up the neck of the bone after passing under the attachment of the capsule. The arteries that supply branches to the hip joint are the:

medial circumflex
lateral circumflex
obturator
inferior gluteal

Movements at the Hip Joint

Movements which take place at the hip joint are:

flexion, mainly due to contraction of the iliopsoas muscle, with help from sartorius, rectus femoris and pectineus.
extension, chiefly by the gluteus maximus muscle with help by the hamstrings
adduction, by the adductors longus, brevis, magnus and the gracilis
lateral rotation, by gluteus maximus, quadratus femoris, piriformis, obturator internus and externus, gemelli.
medial rotation, by anterior part of the gluteus minimus and medius and tensor fasciae latae muscles

Nerves to hip joint

The hip joint is supplied by the:

femoral
obturator
sciatic
nerve to quadratus femoris
direct branches of sacral plexus

Knee Joint

The knee joint is an articulation between the condyles of the femur and of the tibia as well as the lower end of the femur and the patella. The articulation between the femur and tibia is essentially a hinge joint with a very small amount of rotation possible. The articulation between the femur and patella is a plane joint where the patella glides on the femur.

The condyles of the tibia are separated by the intercondylar eminence. There are anterior and posterior condylar areas that serve as attachments to the anterior and posterior cruciate ligaments, respectively.

By now you have learned about many of the large and strong muscles that arise or insert into the bones that make up the knee joint. The quadriceps femoris attaches into the patella and from that into the tibia via the patella ligament. The vastus lateralis and medialis part of this muscle strengthens the capsule of the knee joint. If part of the capsule is removed, you can identify the tibial collateral capsular ligament. This capsular ligament is fixed to the medial meniscus and is therefore more prone to be involved in certain sports injuries. Note that there is a fairly large fat pad beneath the patella. Usually this will provide freedom of movement between the patellar ligament and the bony knee structures allowing for compression and decompression in this area.

Looking at the lateral aspect of the knee joint you can appreciate the attachment of very strong iliotibial tract. Remember that this is tensed by the tensor fasciae latae muscle. From the lateral view, you can also identify the tendon of the very strong biceps femoris muscle which attaches into the head of the fibula.

Also note the fibular collateral ligament. Specifically notice that this ligament if free from the capsule of the knee joint and, therefore, is not as likely to be injured in knee injuries occurring during games such as football.

By observing the posterior aspect of the knee joint, identify the arcuate popliteal ligament This ligament arches upwards and medially over the popliteus from the head of the fibula. Note that the tendon of the popliteus is attached to the lateral epicondyle of the femur just deep to the attachment of the fibular collateral ligament.

By removing the two heads of the gastrocnemius muscle and the vessels and nerves in the area, you can identify the oblique popliteal ligament.

When the patella is cut away from the quadriceps muscle and reflected downwards, you can see the internal makeup of the knee joint. Note first that there is a small muscle that arises from the lower anterior surface of the femur and attaches into the upper part of the joint capsule. This is the articularis genu muscle.

Also notice the small fold of tissue that lies deep to the patella when it is in its normal position, the synovial infrapatellar fold

When the knee is flexed and the various synovial folds are removed, you can see the inner structures making up the knee joint. You should be able to identify the:

anterior cruciate ligament
posterior cruciate ligament
lateral meniscus
medial meniscus - firmly attached to the tibial collateral ligament
transverse ligament
fibular (lateral) collateral ligament
tibial (medial) collateral ligament (not names on image)

From the posterior view of the knee joint you should be able to identify the:

anterior cruciate ligament
posterior cruciate ligament
medial collateral ligament
lateral collateral ligament
arcuate popliteal ligament
posterior meniscofemoral ligament

Movements of the Knee Joint

The main movement at the knee joint it flexion and extension. However, it is a little more complex than this because the AP axes of the medial and lateral femoral condyles are slightly different as well are their size. When the knee is bent with the foot on the ground, some rotation of the distal end of the femur is possible on the upper end of the tibia. Such voluntary rotation is possible only when the joint is flexed because this is the only position in which the tibial collateral, fibular collateral and cruciate ligaments of the joint are not tense. When the knee is flexed and the ligaments are loose, the knee has a tendency to fall off the tibia if it weren't for the cruciate ligaments which prevent this movement. The posterior cruciate prevents the movement of the femur forward on the tibia and the anterior cruciate prevents the the movement backward.

There are several muscles that flex the leg at the knee joint:

hamstring muscles
sartorius
gracilis
gastrocnemius

The main extensor is the quadriceps femoris muscle. The muscle that locks the knee into full extension is the tensor fasciae latae and gluteus maximus by way of the iliotibial tract.

To break full extension and start flexion, the popliteus muscle is called into action. This muscle pulls on the lateral condyle of the femur causing it to laterally rotate.

During the normal stages of walking, the knee is extended during the swing through phase and flexed during the push off phase. When the knee is extended during walking, the foot is laterally rotated. This makes sense because if it rotated medially, you would trip over your own feet. So lateral rotation of the tibia and therefore the foot is a normal function.

Ankle Joint

The ankle joint is an articulation between the tibia, fibula and talus. It is a synovial hinge joint with only two movements possible, dorsiflexion (extension) or plantarflexion (flexion).