Knee, Politeal Fossa and lower Leg

Question 1

What are the borders of the popliteal fossa and its contents?

Answer 1

Borders: Medial border – lateral side of the semimembranosus and semitendinosus and the medial head of gastrocnemius, lateral border – long head of biceps femoris and Plantaris, floor – knee joint capsule and the roof of deep fascia.

Contents include: popliteal artery and vein, small saphenous vein (exits via the deep fascia, tibial nerve and common peroneal nerve.

Question 2

Describe the knee joint

Answer 2

Knee joint is a large synovial hinge joint – 2 articulations tibia and femur and femur and patellar. Medial condyle of femur is larger and takes more weight, all lined with hyaline cartilage. 2 fibrocartilaginous menisci within the joint deepens the sockets the femur sits into. Synovial membrane covers all except the cruciate ligaments, and is separated from the patellar ligament by an infrapatellar fat pad and alar folding in the membrane.

Question 3

What are the 3 main bursa in the knee joint

Answer 3

There are 3 main bursa allowing for frictionless movement of important tendons: Subcutaneous and deep infrapatellar bursa surrounding the patellar ligament and the prepatellar bursa which sits on the anterior surface of the patella.

Question 4

Where is the joint capsule slightly lacking

Answer 4

Joint capsule lacking on anterior side to allow for correct bursa to form.

Question 5

Which muscles stabilise the knee joint?

Answer 5

Joint stabilised laterally by fibres of vastus lateralis and medialis tendons and medially by Goose’s foot (Sartorius, Gracilis and semitendinosus).

Question 6

How does the knee allow us to stand up for long periods of time without tiring?

Answer 6

Knee joint locks into place when fully extended by femur internally rotating over the tibia (unlocked by popliteus muscle).

Question 7

Describe the ligaments of the knee joint

Answer 7

Ligaments – patellar ligament, lateral and medial collateral ligaments (medial also attached to medial menisci) and two cruciate ligaments – anterior one goes from anterior middle tibial to lateral posterior intercondylar fossa of femur whilst posterior comes from posterior and attaches medially and anteriorly.

Question 8

Is the tibiofibular joint contained within he knee joint?

Answer 8

Tibiofibular joint not in knee joint.

Question 9

How is the tibiofibular joint stabilised?

Answer 9

Contains anterior and posterior ligaments to stabilise.

Question 10

What is the unhappy triad?

Answer 10

Unhappy triad – medial collateral and medial menisci are firmly attached so often damaged together and ACL is usually involved as well.

Question 11

Which movement do each cruciate ligament limit

Answer 11

Posterior - hyperflexion

Anterior - extension

Question 12

When is the PCL usually damaged?

Answer 12

PCL usually damaged when falling on the tibial tuberosity with a flexed knee.

Question 13

How can the patella be damaged?

Answer 13

Patellar can be fractured or dislocated (usually laterally)

Question 14

What sort of pathology is common in roofers and tilers?

Answer 14

Chronic bursitis

Question 15

Why is OA so common in knees?

Answer 15

OA very common due to large weight bearing role.

Question 16

What are baker’s/popliteal cysts?

Answer 16

Baker’s cysts/Popliteal cysts are abnormal fluid filled protrusions of the synovial membrane in the popliteal fossa. It is a sign of chronic effusion.

Question 17

Describe the compartmentalisation of the lower leg muscles

Answer 17

Three muscle compartments separated by an interosseous membrane and 2 intermuscular septa.

Question 18

There are two openings in the interosseous membrane - what passes through them?

Answer 18

Two openings in the interosseous membrane: top for anterior tibial vessels and bottom for perforating branch of fibular artery.

Question 19

How does achilles tendon damage usually occur

Answer 19

Achilles Tendon rupture usually due to direct trauma. Can find obvious gap in the tendon and if you squeeze the calves whilst kneeling on a chair there is no movement (Thompson’s test).

Question 20

Why does foot drop occur?

Answer 20

Foot drop occurs due to lack of dorsiflexion which is due to damage to the common fibular nerve. Long term pressure on this nerve can cause temporary paralysis.

Question 21

Describe some common fracture of the leg

Answer 21

Stress fracture of tibia can occur due to repetitive force causing shin splints.

Subcondylar fracture of the tibia commonly occurs in a car crash when the flexed knee hits the dashboard.

Fallowing on inverted foot = lateral malleolus fracture, on everted foot = tibial malleolus.

Question 22

Describe the two common types of bursitis?

Answer 22

Housemaids bursitis – pre patellar burisits. Clergyman’s bursitis – infrapatellar bursitis.

Question 23

What is one potential differential diagnosis for a popliteal cyst?

Answer 23

Popliteal aneuryms – swelling behind the knee of the popliteal artery.