Knee + Shoulder, Elbow B&B

Question 1

the ACL runs from the ____ to the _____
the PCL runs from the ____ to the _____

Answer 1

the ACL runs from the lateral femoral condyle to the anterior tibia

the PCL runs from the medial femoral condyle to the posterior tibia

Question 2

valgus vs varus deformities of the knee are resisted by which ligaments, respectively?

Answer 2

valgus = knock-kneed (lower leg abducted), resisted by MCL (medial collateral ligament)

varus = bow-legged (lower leg adducted), resistant by LCL (lateral collateral ligament)

Question 3

the MCL runs from the ____ to the ____
the LCL runs from the ____ to the ____

Answer 3

the MCL runs from the medial epicondyle of the femur to the medial condyle of the tibia

the LCL runs from the lateral condyle of the femur to the head of fibula

Question 4

a positive “anterior drawer sign” is diagnostic of what kind of tear?

Answer 4

ACL injury

when patient is supine, bend knee at 90* angle and pull tibia forward - if forward movement is greater than normal there is an ACL tear, because the ACL resists anterior forward movement of tibia

Question 5

what is the classic cause of a PCL tear?

Answer 5

“dashboard injury” - due to car crash, knee gets thrown into dashboard, which causes lower leg to get pushed back

PCL tears often occur via trauma/force directed posteriorly at knee (contrast to ACL tears which area usually due to change of direction, non-contact)

Question 6

what is the McMurray Test used for?

Answer 6

diagnosing meniscus tear

while patient is supine, the bent knee is held and extended while rotating the foot - if there is pain or a “pop” sound, there is a tear

internal rotation of the tibia tests lateral meniscus, external rotation of tibia tests medial meniscus

Question 7

what kind of joint is the knee?

Answer 7

synovial - contains synovial fluid inside membrane, surrounded by bursa

there are 4 bursa around the knee

Question 8

A woman presents to her GP with knee pain. On PE, the knee appears swollen and warm anterior to the patella. The patient says the pain comes with activity. She works as a housemaid. What is the most likely diagnosis and how can it be treated?

Answer 8

prepatellar bursitis - “housemaid’s knee” because it is often caused by repeated kneeling, can also be caused by infection or gout

treat with NSAIDs

Question 9

where do Baker’s Cysts occur?

Answer 9

aka popliteal cysts, occur when fluid collects in the gastrocnemius-semimembranosus bursa at the back of the knee

often communicates with synovial space, related to chronic joint disease/ common in patients with rheumatoid arthritis

rupture may cause acute pain that mimics DVT

Question 10

Patient with PMH of rheumatoid arthritis presents to the ED with acute leg pain. A colleague of yours is worried it may be DVT, though you think imaging will reveal…

Answer 10

Baker’s Cyst: aka popliteal cysts, occur when fluid collects in the gastrocnemius-semimembranosus bursa at the back of the knee

common in patients with rheumatoid arthritis, rupture may cause acute pain that mimics DVT

Question 11

Osgood-Schlatter Disease

Answer 11

aka tibial tuberosity avulsion - pain/swelling at tibial tuberosity that occurs in children due to overuse

tibial tuberosity is insertion point of patellar tendon and secondary ossification center of tibia

benign, self-limited

Question 12

what can patients with a patellar fracture NOT do?

Answer 12

extend knee against gravity

this is because patella connects quads tendon above to patellar ligament below, which attaches to lower leg - if there is a fracture, the force cannot be transmitted across the knee

Question 13

what are the 4 muscles of the rotator cuff?

Answer 13

1. supraspinatus - initiates abduction, most common rotator cuff injury
2. infraspinatus - assists in external rotation and abduction
3. subscapularis - assists in internal rotation of shoulder/arm
4. teres minor - assists in external rotation and adduction

Question 14

tendonitis of the rotator cuff will cause pain with [adduction/abduction]

Answer 14

abduction - the rotator cuff prevents the shoulder from popping out when the arm is moved away from midline

Question 15

what is the most commonly injured muscle of the rotator cuff and how does this typically occur?

Answer 15

supraspinatus - initiates abduction (away from midline), injury usually via impingement of tendon between humeral head and acromion process of scapula

“swimmer’s shoulder” or “thrower’s shoulder”

Question 16

what does the empty/full can test diagnose?

Answer 16

identifies supraspinatus injury, most common injury of rotator cuff, usually via impingement

empty can test (arm out and slightly in front with thumb down) / full can test (arm with thumb up) —> pain with pressing down = positive test

Question 17

which nerves innervate each muscle of the rotator cuff? (4)

Answer 17

1. supraspinatus - suprascapular nerve
2. infraspinatus - suprascapular nerve
3. teres minor - axillary nerve
4. subscapularis - upper/lower subscapular nerves

all come from brachial plexus!

Question 18

which 3 muscles are involved in shoulder abduction, and what are their respective roles?

Answer 18

1. supraspinatus - initiates abduction, first 15 degrees
2. delotid - primary abductor, up to 90 degrees
3. trapezius/serratus anterior - abduction beyond 90 degrees

Question 19

shoulder dislocations commonly injure which nerve? which muscle will this affect most?

Answer 19

axillary nerve - runs below humeral head and wraps around neck of humerus

causes sensory loss of deltoid muscle —> weak abduction

Question 20

tennis elbow vs golfer’s elbow

Answer 20

tennis elbow - lateral epicondylitis of humerus, elbow pain with resisted wrist extension

golfer’s elbow - medial epicondylitis of humerus, elbow pain with resisted wrist flexion

Question 21

nursemaid’s elbow

Answer 21

aka radial head subluxation (partial dislocation)

caused by axial traction on pronated forearm (like a child yanking on an arm) —> annular ligament slips over head of radius and becomes trapped in radiohumeral joint

Question 22

most common pediatric elbow fracture

Answer 22

supracondylar fracture - just above condyles, in distal part of humerus (just above elbow joint)

brachial artery and median nerve may be injured!