Workbook questions 9 & 10

Question 1

Explain the significance of the process of “locking and unlocking” of the knee?

Answer 1

When the knee is fully extended with the leg and foot on the ground, the knee “locks” because of medial rotation of the femur on the tibia. This movement enables the lower limb to become a solid column to support the weight of the body. In the locked position, the thigh and leg muscles relax without making the knee joint unstable.

In order to flex the knee, the knee has to “unlock”; this is done by contracting the popliteus muscle which results in rotating the femur laterally on the tibia so that flexion of the knee can take place

Question 2

State the tissue and shape of the menisci of the knee joint and also give two functions.

Answer 2

The menisci are crescent-shaped fibrocartilaginous plates that are found on the articular surface of the tibia. They help in deepening the articular surface and also act as shock absorbers.

Question 3

Footballers often have to undergo surgery for removal of one or both the menisci. Which one is the most common meniscus to be torn and why?

Answer 3

The medial meniscus is the most commonly torn of the two menisci of the knee joint. This is because it is firmly adherent to the tibial (or medial) collateral ligament. Although the tibial collateral ligament is broad, it is weaker than the fibular (or lateral) collateral ligament which is a strong round band of tissue.

Excessive or violent trauma on the lateral aspect of the knee (e.g. a kick administered during a game of football) may result in excessive medial displacement of the tibia causing the tibial collateral ligament to tear/rupture and a concomitant tearing of the medial meniscus.

Question 4

Why might a “locked” knee be the presenting sign of a torn meniscus?

Answer 4

A torn meniscus may result in it becoming dislodged (or its fragment breaking away) and becoming trapped within the knee joint cavity causing the knee to become “locked”.

Question 5

What are “housemaid’s knee” and “clergyman’s knee”?

Answer 5

“Housemaid’s knee” is the inflammation of the prepatellar bursa; the bursa becomes distended with fluid and forms a swelling anterior to the knee. Prepatellar bursitis usually results from friction caused by excessive rubbing
of the skin against the patella.

“Clergyman’s knee” is the inflammation of the subcutaneous infrapatellar bursa; the bursa becomes distended with fluid as a result of excessive friction between the skin and tibial tuberosity. The oedema occurs over the proximal end of tibia.

Question 6

What are the ‘Drawer’ tests and what do they show?

Answer 6

They are performed by pulling the leg forward or backward with the knee in flexed position (90°).

The examiner should sit close to the foot to steady it. The leg is grasped below the knee with both hands and the tibia pulled forward. Abnormal mobility suggests rupture of the anterior cruciate ligament. Similarly, backward displacement of the tibia with abnormal mobility would suggest posterior cruciate ligament rupture.

Question 7

Label the following on a diagram quadriceps muscle tendon
patellar ligament
patella
prepatellar
suprapatellar bursa.
Medial and lateral femoral condyles
tibial tuberosity, head of fibula
medial and lateral meniscus
lateral (fibular) collateral ligament
medial (tibial) collateral ligament
anterior cruciate ligament

Answer 7

See notes/ book

Question 8

A pulled hamstring” is a common sporting injury. Explain the structural and
functional basis of such an injury.

Answer 8

This injury is common in persons who undertake activities that require violent or sudden muscular exertion.
In this case there is tearing (part/complete) of tendinous attachments of the hamstrings to the ischial tuberosity resulting in the rupture of blood vessels supplying the muscles.

Question 9

Why is a popliteal pulse difficult to feel even in the normal individual?

Answer 9

The popliteal artery lies quite deep in the popliteal fossa; the artery lies deep to the popliteal vein and the tibial nerve. With the knee is full extension, the skin and the underlying fascia become taut and make it difficult to feel the pulsations of the popliteal artery. In order to feel the pulse, the knee has to be in flexion and the fingers pressed firmly into the popliteal fossa to press the artery against the posterior aspect of the femoral intercondylar area to feel the pulse.

Question 10

List four structures that you think may be the cause of a swelling in the region of the popliteal fossa?

Answer 10

The following structures can cause a swelling in the popliteal fossa: popliteal aneurysm, (will be pulsatile swelling) popliteal (Baker’s) cyst (formed as a result of herniation of the synovial membrane of the knee joint), an abscess, tumour and enlarged lymph nodes.

Question 11

What is the difference between a simple and compound fracture, and explain why which of these fractures poses a greater risk of infection?

Answer 11

In simple fracture, the overlying skin is healthy and closed. In compound fracture, the overlying skin is breached and the fracture site is itself exposed to the outside environment. The compound fracture poses a greater risk of infection.

Question 12

When can a fracture be described as being pathological?

Answer 12

A pathological fracture is one in which the fracture occurs through a bone already weakened by underlying disease (e.g. brittle bone disease, osteocarcinoma, osteoporotic bone, cysts, etc.)

Question 13

What causes a stress fracture?

Answer 13

In these fractures (also termed as ‘fatigue fractures’) the bone is fatigued by repetitive stress; common example is a fracture of the second metatarsal in young adults who walk long distances, tibial fractures in long distance runners & hurdlers.

Question 14

In bone fractures, explain what is callus and what is its function?

Answer 14

The fibroblasts in the granulation tissue (haematoma at the site of the fracture) undergo metaplasia and change into chondroblasts. The chondroblastic tissue forms islets of cartilage around collagen fibres; this mass of tissue is called ‘callus’ which temporarily helps to bind the two bone ends together.

Question 15

Describe the action of muscles in the anterior and lateral compartments of the leg.

Answer 15

Tibialis anterior, extensor hallucis longus, extensor digitorum longus & peroneus (fibularis) tertius all dorsiflex the ankle.

Tibialis anterior also inverts the foot at the subtalar joint. Peroneus (fibularis) tertius everts the foot at the subtalar joint.

Extensor hallucis longus extends the great toe and extensor digitorum longus extends the lateral four digits.

Question 16

In general what is the function of the retinacula around the ankle region?

Answer 16

The extensor retinacula bind down the tendons of the muscles in the antero-lateral compartments and prevent them from bowstringing during movements at the ankle.

Question 17

With reference to local anatomy, where in the foot would you be able to palpate the pulse of the dorsalis pedis artery?

Answer 17

The dorsalis pedis artery is the continuation of the anterior tibial artery (a branch of the popliteal artery ) into the dorsum of the foot. Its pulsation can be felt between the tendons of extensor hallucis longus and the medial most tendon (going to the 2nd digit) of the extensor digitorum longus muscle.

Question 18

A traumatic injury to the leg may lead to a condition called “compartment syndrome”. How does this syndrome occur and what are the short and long-term consequences of such a disorder?

Answer 18

The limbs are organised into compartments which are bounded by bone and deep fascia and contain muscles with their nerve and blood supply together with nerves and vessels to more distal parts of the limb. Muscle within the fascial compartment is perfused by blood. Trauma to the fascial compartment may rupture the blood vessels and cause a temporary rise in compartmental tissue pressure. If a sustained rise in tissue pressure is above the arterial perfusion pressure, muscle and nerves will be deprived of blood supply. Ischemic muscle releases factors which increase capillary permeability and worsen the situation.

Nerve fibres are susceptible to ischemia; the thin cutaneous nerve fibres are affected more than the motor fibres, which causes distal paraesthesia before motor function.

Question 19

Where in the ankle region would you be able to find the great (long) and lesser (short) saphenous vein?

Answer 19

The great (long) saphenous vein runs above (anterior to) the medial malleolus while the lesser (short) saphenous vein runs behind (posterior to) the lateral malleolus. Unlike other superficial veins in the body, the great saphenous vein is considered to be one of the superficial veins that is relatively constant in location.

Question 20

After a “cut down procedure” for insertion of an intravenous line into the great (long) saphenous vein, patient complained of numbness and loss of sensation
on the medial aspect of the foot. What is the explanation of this occurrence?

Answer 20

The saphenous nerve, which is a sensory branch of the femoral nerve, runs in close proximity to the long saphenous vein in the leg. Insertion of an intravenous line into the vein and in the attempt to secure the line with a ligature may compress the nerve leading to disturbances in sensory supply to relevant region.

Question 21

Give two reasons a “kick on the shin” hurt so much? (Hint consider local tissue and the nerve supply to the bone)

Answer 21

The surface of the tibia along most of the medial aspect of the leg has only subcutaneous soft tissue. The bone is covered by periosteum which has a rich nerve supply.

Question 22

Look up intermittent claudication. What factors in a patients history might make them a likely candidate for this condition?

Answer 22

History of arterial disease (coronary by-pass)
Risk factors for arterial disease: smoking
diabetes possible high fat/high salt diet (pre-prepared
meals)
Age

Question 23

List the pulses in the lower limb and state in anatomical terms where they are palpable

Answer 23

Femoral artery: Mid-inguinal point.
Popliteal artery: Popliteal fossa.
Posterior tibial artery: Behind medial malleolus
Dorsalis pedis artery: Dorsum of the foot between tendons of extensor hallucis longus and extensor digitorum

Question 24

On examination, you find that on the right side, the posterior tibial arterial pulse is normal whereas the dorsalis pedis pulse is diminished; what do you conclude from this?

Answer 24

Occlusion has most likely occurred in the anterior tibial artery; posterior tibial artery is patent.

Question 25

On the left-hand side, you find the same features (diminished dorsalis pedis pulse and normal posterior tibial arterial pulse) however the patient isn’t complaining of any symptoms. Give two possible reasons for these findings?

Answer 25

1. Occlusion has also occurred in the left anterior tibial artery, but this is asymptomatic
2. Congenitally absent dorsalis pedis pulses.

Question 26

Whilst waiting for an angioplasty, the man develops an acute arterial occlusion due to blood clots in his right popliteal artery. What signs and symptoms will be present in his leg?

Answer 26

The 6 “P’s”: pain, paraesthesia, pallor, perishingly cold,’ pulselessness’, paralysis (weakness)