Finishing off the joints

Question 1

What are the ligaments of the hip?

Answer 1

The ligaments of the hip joint act to increase stability. They can be divided into two groups – intracapsular and extracapsular.

Question 2

What are the intracapsular joint of the hip?

Answer 2

The only intracapsular ligament is the ligament of the head of the femur. It is a relatively small structure, which runs from the acetabular fossa to the fovea of the femur.
It encloses a branch of the obturator artery, a minor source of arterial supply to the hip joint.

Question 3

What are the extracapsular joints of the hip?

Answer 3

Iliofemoral ligament – arises from the anterior inferior iliac spine and then bifurcates before inserting into the intertrochanteric line of the femur (prevents hyperextension)
Pubofemoral – spans between the superior pubic rami and the intertrochanteric line of the femur, reinforcing the capsule anteriorly and inferiorly (prevents excessive abduction and extension)
Ischiofemoral– spans between the body of the ischium and the greater trochanter of the femur, reinforcing the capsule posteriorly (prevents hyperextension)

Question 4

What is the hip joint?

Answer 4

The acetabulum is the socket and the bones of the pelvis form a complete hemisphere.
Round the edge of the hemisphere is a fibro-cartilaginous labrum (lip) which narrows round the head of the femur.

Question 5

What is Perthes disease?

Answer 5

In children the femoral epiphysis receives its blood supply through this nutrient artery and if it provides insufficient blood the femoral head will undergo avascular necrosis (it will die), this is Perthes disease.

Question 6

What are the consequences of a fracture of the neck of the femur?

Answer 6

In the adult the femoral head receives all of its blood along the neck of
the femur. In patients with fracture of the neck of the femur the femoral head may also undergo avascular necrosis and require surgical replacement.

Question 7

What are the ligaments of the knee?

Answer 7

Medial collateral ligament - this stops valgus
movement of the tibia (angulation of the knee away from the midline).
Lateral collateral ligament - stops
varus movement of the knee (angulation of the knee towards the midline).
Anterior and posterior cruciate ligaments - stop
forwards and backwards movement of the tibia on the femur respectively.

Question 8

At 90 degrees, 30 degrees and full extension, what movement can occur at the knee?

Answer 8

With the knee flexed at 90 degrees all four of these ligaments are lax, they have no tension within them. This means that the tibia is ‘loose’ on the femur, it cannot move very far, but it can move.
At 30 degrees of flexion the anterior cruciate ligament has become taught, the others are still lax. Any abnormal force passing through the knee, eg. Twisting, will pass through the anterior cruciate ligament and it may rupture.
In full extension all the ligaments at taught and any force is distributed between the ligaments and less likely to cause rupture.

Question 9

Why does twisting occur in the knee joint?

Answer 9

This twisting is due to the shape of the articular surfaces and the anterior cruciate ligament.
When the knee is fully extended it ‘locks’ and all the body weight can be supported without
the action of muscles. In order to ‘unlock’ popliteus muscle ‘untwists’ the knee and flexion
can occur.

Question 10

What are the articulations of the knee?

Answer 10

Tibiofemoral – medial and lateral condyles of the femur articulate with the tibial condyles. It is the weight-bearing component of the knee joint.
Patellofemoral – anterior aspect of the distal femur articulates with the patella. It allows the tendon of the quadriceps femoris (knee extensor) to be inserted directly over the knee – increasing the efficiency of the muscle.

Question 11

What is the fulcrum of the knee?

Answer 11

As the patella is both formed and resides within the quadriceps femoris tendon, it provides a fulcrum to increase power of the knee extensor, and serves as a stabilising structure that reduces frictional forces placed on femoral condyles.

Question 12

What are the menisci of the knee?

Answer 12

Two fibrocartilaginous crescents which fill the gap

between the curved femoral condyles and the relatively flat tibial plateaux.

Question 13

What is the lateral menisci of the knee like?

Answer 13

The lateral condyle of the femur needs to roll forwards on the tibia so the lateral meniscus is only connected at its ends. The means that the lateral meniscus is mobile and can move with the femoral condyle.

Question 14

What is the medial menisci of the knee like?

Answer 14

The medial femoral condyle only slides over a fixed point of the tibia and the medial meniscus does not need to be mobile, it is attached over its entire circumference to the capsule of the knee.

Question 15

How can twisting the knee cause a tear in the menisci?

Answer 15

If an abnormal twist is put on the knee, in any position, the lateral meniscus can move
with the twist. However, the medial meniscus is fixed and the force of the femur moving over
the meniscus can cause a tear.

Question 16

What is a bursa?

Answer 16

A bursa is synovial fluid filled sac, found between moving structures in a joint – with the aim of reducing wear and tear on those structures. There are four bursae found in the knee joint.

Question 17

What are the different bursa in the knee?

Answer 17

Suprapatella bursa – This is an extension of the synovial cavity of the knee, located between the quadriceps femoris and the femur.
Prepatella bursa – Found between the apex of the patella and the skin.
Infrapatella bursa – Split into deep and superficial. The deep bursa lies between the tibia and the patella ligament. The superficial lies between the patella ligament and the skin.
Semimembranosus bursa – Located posteriorly in the knee joint, between the semimembranosus muscle and the medial head of the gastrocnemius.

Question 18

What is the ankle?

Answer 18

The ankle is the joint between the tibia and fibula with the talus of the foot.

Question 19

What is a sprained ankle?

Answer 19

‘Sprained’ ankle is common and is caused by tears in the ligaments of the ankle.

Question 20

What are the ligaments of the ankle?

Answer 20

Delta ligament - ‘D’ shaped ligament which has a broad attachment from the malleolus, attaching to the talus, calcaneus and navicular bones.
Resists over-eversion.
There are two ligaments connecting the fibula to the talus one running anteriorly and one posteriorly, the anterior and posterior talofibular ligaments. Between them is a single ligament from the fibular to the calcaneus the calcaneofibular ligament.
Resists over-inversion.

Question 21

What movements occur at the ankle joint?

Answer 21

The ankle joint is a hinge type joint, with movement permitted in one plane.
Thus, plantarflexion and dorsiflexion are the main movements that occur at the ankle joint. Eversion and inversion are produced at the other joints of the foot, such as the subtalar joint.

Question 22

What is plantarflexion and dorsiflexion?

Answer 22

Plantarflexion – produced by the muscles in the posterior compartment of the leg (gastrocnemius, soleus, plantaris and posterior tibialis).
Dorsiflexion – produced by the muscles in the anterior compartment of the leg (tibialis anterior, extensor hallucis longus and extensor digitorum longus).

Question 23

How are the tibia and fibular joined?

Answer 23

The tibia and fibula are connected to each other by the superior and the inferior tibiofibular
joints as well as by the interosseous membrane.

Question 24

What stabilises the ankle joint?

Answer 24

The medial and lateral malleoli which grip the sides of the talus along with the ligaments and
the muscles crossing the joint stabilise the ankle joint.

Question 25

Where does the talus bone slot in?

Answer 25

The joint surfaces of the tibia and fibula, along with the malleoli, form a mortice to receive the talus.

Question 26

What happens in a fracture of the neck of the femur?

Answer 26

In the adult the blood vessels which supply the head of the femur travel along the neck of the femur. Osteoporosis is a common condition in the elderly particularly in females, and it results in brittle bones. Falls in the elderly are often onto the ‘hip’ and this results if a fracture of the neck of femur (#NOF). The fracture interrupts the blood supply to the head of the femur which will need to be surgically removed and replaced.

Question 27

What happens in a cruciate ligament tear?

Answer 27

The ligaments of the knee are all ‘loose’ when the knee is bent to 90 degrees and all tight when the knee is straight. However, at about 30 degrees of flexion there is only one ligament which is taught, the anterior cruciate. If an abnormal force is experienced by the knee in this position the anterior cruciate may not be strong enough and it will rupture.

Question 28

What happens in a medial meniscus tear?

Answer 28

The lateral meniscus is attached to the tibia at the two ends of the meniscus, this enables it to move when a rotating force is experienced by the knee. Conversely the medial meniscus is attached to the capsule of the knee all the way around its perimeter. The result is that the medial meniscus cannot move when an abnormal twisting force is experienced and it may get torn.

Question 29

What happens in a sprained ankle?

Answer 29

The ankle is held together with a complex of medial and three lateral ligaments. If the ankle is subjected to a forced inversion or eversion, then these ligaments may tear, this is a sprained ankle.

Question 30

What happens at the Subtalar joint?

Answer 30

Talus articulates with the calcaneus and the navicular bone.

Question 31

What happens at the Midtarsal joint?

Answer 31

The anterior surface of the head of the talus articulates with the navicular bone. This along with the joint between the calcaneus and the cuboid (calcaneocuboid joint) make up the midtarsal joint.

Question 32

What is eversion and inversion?

Answer 32

Eversion - the lateral border of the foot is slightly raised, making the sole of the foot face laterally.
Inversion - the sole of the foot faces medially.
Most of these movements take place in the subtalar joint.

Question 33

What are the main invertors and evertors of the foot?

Answer 33

Tibialis anterior and the tibialis posterior invert the foot.
Peroneus longus and brevis are the main evertors.

Question 34

What joints move during inversion and eversion of the foot?

Answer 34

As the muscles involved are attached beyond the midtarsal joint in the early part of inversion and eversion the midtarsal joints also move.
In inversion the midtarsal joint adducts and in eversion it abducts. When the foot is on the ground, adduction of the forefoot is masked by lateral rotation of the leg.
Similarly, eversion of a fixed foot is accompanied by medial rotation of the leg.

Question 35

What are the major nerves that come from the lumbar plexus?

Answer 35

Femoral: L2-4 emerging laterally from Psoas. It passes under the inguinal ligament to enter the anterior thigh.
Obturator: L2-4 emerging medially from psoas. It passes through the obturator canal to enter the medial compartment of the thigh.
Sciatic - L4 and L5 join S1-3 to form the sciatic nerve.
The sciatic is composed of the tibial nerve and the common peroneal nerve.
The common peroneal nerve divides into the superficial and deep peroneal nerves.
The Tibial nerve has branches in the foot, the medial and lateral plantar nerves.

Question 36

What is the lateral cutaneous nerve of the thigh?

Answer 36

The lateral cutaneous nerve of the thigh that passes behind the inguinal ligament to supply skin on the lateral part of the thigh. Compression of this nerve would result in altered sensation felt laterally.

Question 37

What are the major compartments of the thigh?

Answer 37

Anterior thigh - ‘the Quads’ extensors of the knee, innervated by the femoral nerve
Medial thigh - adductors of the hip, innervated by the obturator nerve (obturator supplies a small portion of medial skin too)
Posterior thigh - ‘the hamstrings’ flexors of the knee, innervated by the sciatic nerve

Question 38

Which nerve supplies the posterior compartment of the thigh?

Answer 38

Most of the posterior compartment of the thigh is supplied by the tibial part of the sciatic, exception short head of biceps femoris.

Question 39

What is the nerve supply of the adductor magnus?

Answer 39

The adductor magnus is part hamstring and adductor, therefore nerve supply both obturator and tibial portion of the sciatic.

Question 40

What are the compartments of the leg?

Answer 40

Posterior leg - plantar flexors of the ankle, flexors of the toes, innervated by the tibial nerve
Lateral leg - evertors of the foot, innervated by the superficial peroneal, supplies most of skin on the dorsal surface of the foot
Anterior leg - dorsiflexors of the ankle, extensors of the toes, innervated by the deep peroneal nerve, supplies a small area of skin between the big toe and second toe

Question 41

What is the medial plantar nerve?

Answer 41

Equivalent to the median nerve of the hand
Supplies most of the muscles of the big toe, except the adductor. On the sole of the foot it supplies the skin of three and a half toes, starting from the big toe.

Question 42

What is the lateral plantar nerve?

Answer 42

Equivalent to the ulnar nerve of the hand

Supplies most of the small muscles of the foot. Skin on the sole of the foot, the lateral one and a half toes.

Question 43

Why is rectus femoris different to the other Quads?

Answer 43

Rectus femoris (part of the quads) both flexes the hip and extends the knee.The rest of the quads, vastus medalis, lateralis and intermedius extend the knee only.

Question 44

What is referred pain in the knee and hip?

Answer 44

Appreciate that the hip and knee are innervated by the same nerves - femoral, obturator, sciatic (common peroneal, tibial nerve).
Therefore a patient complaining of knee pain may actually have disease in the hip (referred pain).

Question 45

Which of the menisci are more likely to be damaged?

Answer 45

In damage to the mensci of the knee, more commonly it is the medial mensci that is damaged.
The medial mensci is attached to the capsule of the knee and cannot move when abnormal forces are loaded onto the knee.

Question 46

How does a fracture of the femur affect the presentation of the leg?

Answer 46

A fractured neck femur leads to a shortened, laterally rotated leg.

Question 47

What movements occur at the ankle joint?

Answer 47

Ankle movements - dorsiflexion and plantarflexion only.
Inversion/eversion occur at the subtalar joints.
Eversion - peroneus longus and brevis.
Inversion - Tibialis Anterior and posterior.

Question 48

What is foot drop?

Answer 48

The common peroneal nerve is superficial around the head of the fibular. Imagine a plaster cast that has been applied too tightly around the leg. The common peroneal supplies both the anterior and lateral compartments of the leg. Compression of this nerve will lead to the loss of DF at the ankle. As the foot is lifted it will plantar flex, as this is the only muscle group that is working, hence foot drop.

Question 49

When does the femoral artery become the popliteal artery?

Answer 49

the Femoral artery becomes the popliteal artery as it goes through the hiatus in Adductor magnus.

Question 50

Where can the anterior and posterior tibial artery be felt?

Answer 50

The posterior tibial artery is felt behind the medial malleolus.
The anterior tibial artery becomes the Dorsalis pedis pulse, felt between the 1st and 2nd metatarsals on the dorsal surface of the foot.