Lower Extremity: Acute Knee Injury

Question 1

what’s going on in this xray

Answer 1

small bone fragment underneath the knee– a BONE CHIP.

• will change in shape and pain– needs to be taken out.

Question 2

wha’ts going on in this knee scope

Answer 2

there is a large osteochondral fragment between the articulation of femur and tibia

Question 3

T/F you can sprain your knee

Answer 3

false. this is an oversimplification. You can tear your ACL or PCL but you need an actual diagnosis to tailor the treatment.

Question 4

treatment of ankle sprain

Answer 4

RICE

Rest, Ice Compression, Elevation

Question 5

A person had a knee injury two years ago and was told they sprained their knee. They returned to soccer after some rest and there has been tweeks in the past where the knee just gives out, but it has never been as bad as the first injury. Now, however, he cannot straighten his knee.

Imaging is as shown. What was missed?

Answer 5

he most likely had a torn ACL. You can see evident meniscus trauma. The torn ACL causes bone shifting. meniscus then takes up the slack of the torn ACL and it’s not meant to have that much loading force on it at all times. it causes meniscal traring and flipping– can block motion which is why he can’t straighten his knee.

Question 6

T/F a knee replacement for bone erosion is the first line treatment in a 42 year old.

Answer 6

false. you must buy time using screws. a 42 year old is not a candidate for knee replacement–they’ll wear through it quickly. they just support the joint and try to remove the pressure.

Question 7

T/F you need an MRI to diagnose an ACL tear

Answer 7

false. MRI makes a dx 95% of the time, but we can’t do it on everyone. there are strict infications for urgent MRI in acute soft knee problems.

Question 8

Indications for Urgent MRI in Acute Soft Tissue KNee Problem

Question 9

locked vs stiff knee

Answer 9

lock: knee won’t fully extend. torn meniscus or torn ACL, could benefit from MRI
stiff: lack of band and strenght. Don’t need an MRI

Question 10

Causes of lock knee.

Answer 10

a locked knee is one where there is an ACUTE MECHANICAL BLOCK to preventing extension with “normal” flexion. Pain and or weakness do not constitute a mechanical block

- a locked knee can be caused by a displaced meniscal tear, a loose body, or a prominent stump of ACL.

• a stiff knee is a knee where tehre is loss of both flexion and extension due to injury, surgery, or arthritis.

Question 11

A joint swells up within the first 2 hours of injury, what is most likely in the joint when aspirating it?

Answer 11

blood. it’s not going to be synovial fluid. It takes a while for synovial fluid to be made. If it swells up the day after, it could definitely be synovial fliuid, but if it is an acute swelling, it’s probably blood.

Question 12

how much synovial fluid does a normal knee have?

Answer 12

3 cc. it normally just wets the surface of the joint. if it’s swollen, it easily has enough to aspirate.

Question 13

what is the contents of synovial fluid and what is it’s function

Answer 13

• it’s ultrafiltrate of blood plasma containing proteins from the blodo plasma mixed with proteins secreted by synovial cells and chondrocytes.

function:
1. lubrication

2. nutrition
3. shock absorption (rheopectic)

Question 14

T/F you should aspirate a joint if you suspect hemarthrosis within 1-2 hours of injury

Answer 14

false. hemarthrosis is blood contained within the acapusle of a joint. there is no need to aspirate if the swelling was prestn within 1-2 hours of injury– sometimes it feels better when the blood is taken out, but that doesn’t treat the underlying cause.

Question 15

you are aspirating a joint that has been swollen for over 4 hours. you see an oily substance in the aspirate. what might be occuring?

Answer 15

if you see fat globules in a joint aspirate, it’s from the bone marrow. there is probably a fracture leaking marrow contents into the capsule.

Question 16

outline the intra-capsular structures– which ones have the capacity to cause hemarthrosis in response to trauma? (SLAMB)

Answer 16

S; synovium: yes

L; ligaments: yes

A; articular cartilage; no

M; meniscus; yes

B; bone yes

• when you see blood in a joint, htink about what structures can bleed when trauma to it occurs. if the articular cartilage is affected you wouldn’t see bleeidng or acute swelling.

Question 17

differential diagnosis of hemarthrosis

Answer 17

1. bleeding disorder– hemophilia A, B, Vwf
2. fracture (bone)
3. extensor mechanism injury
4. meniscus tear
5. ligament tear.

Question 18

T/F if someone has hemarthrosis you should alwasy to PT PTT and INR to rule out bleeding disorder

Answer 18

false. first check history if you suspect a bleeding disorder– bleeding with minor injuries and dental procedures, spontaneous bleeding into joints and muscle ,family history etc. Ask about prior surgeries.
- you don’t need to test for a bleeding disorder if they have a pretty obvious cause of swelling– like fi they were snowboarding and now they have an acute swollen knee– you dont test for VWF– that’s a waste of resources

Question 19

On physical exam, how would you maybe elucidate that the hemarthrosis is caused of a bleeding disorder and not due to an acute joint injury?

Answer 19

if there’s no bruising, point of maximal tenderness, no back story, no imaging findings.

Question 20

what’re the ottawa knee rules for getting a knee xray?

Answer 20

Question 21

would you see bruising in a tibial plateau fracture?

Answer 21

Proximal tibia is broken. The knee capsule might hold the blood in the joint capsule so you might not see bleeding.

Question 22

you might see hemarthrosis in a tibial plateau fracture, but not in a distal tibia fracture. Why?

Answer 22

There will not be blood in the knee. The distal tibia is broken, the blood from shaft probably wont migrate to the knee. Might see bruising on site of trauma.

Question 23

3 most common extensor mechanism injuries (stuff that straightens you knee)

Answer 23

• knee extensors are quads
  1. patellar dislocation
  2. quadriceps tendon rupture
  3. patellar tendon rupture.

Question 24

Bruising, PMT, Special tests and imaging for patellar dislocation?

Answer 24

bruising; maybe

PMT: medial

Special tests; apprehension sign

Imaging; often normal

Can be direct impact, but if there are risk factors like old age or female, it could just be from a twisting injury or getting up off the ground.

Question 25

treatment for patellar dislocation

Answer 25

1st time dislocation: suually non operative

treatment of a recurrent dislocation depends on the cause

1. Alignment
2. bony
3. soft tissue.

Question 26

risk factors of a quadriceps/patellar tendon rupture

Answer 26

1. steroids
2. antibiotics/floxacins
3. age
4. pre-existing tendonitis
5. uremia.

Question 27

what type of movement causes the quadriceps/patellar tendon rupture?

Answer 27

eccentric contraction; lowering something and the muscle/bicep is lengthening but it’s still firing cause it’s not fully disegngaed.

Question 28

eccentric, isometric, concentric contraction

Answer 28

Eccentric contraction: lowering something and the muscle/bicep is lengthening but it’s still firing cause it’s not fully disengaged.
Isometric: muscle contracting but not moving
Concentric: lifting something and the muscle gets shorter

Eccentric contraction can cause a tendon rupture.

Question 29

What would cause a tendon rupture?

Answer 29

• something that is an eccentric contraction
• D

Question 30

which one is normal?

Answer 30

the left one: The distance from knee cap to tibia is WAAAAY too long, an dthe patella is way too far up the femur. It’s like it he patella tendon torn

right: normal

Question 31

Answer 31

Question 32

bruising, PMT, special tests, and Xray findings of a quad tendon rupture/patellar tendon rupture.

Answer 32

Question 33

function of the knee meniscus

Answer 33

Question 34

what is the bucket handle tear

Answer 34

mensical tear where the mensicus flips to the middle of the knee and the piece of cartilage causes a mechanical blockage causing inability to extend.

Question 35

Why are meniscus tears not swollen? will there be bruising?

Answer 35

meniscus tears aren’t very swollen because it has not as diffuse blood supply. There wont’ be bruising bbecause the meniscus is within the synovium so any blood will be clustered into the capsule.

Question 36

If a knee joint is locked, ___ is indicated

Answer 36

MRI is indicated

Question 37

T/F first treatment of torn meniscus is a meniscectomy

Answer 37

false. it leads to SEVERE artritis. tearing your meniscus should be NON operative.

The meniscus is very important to prevent arthritis. It’s usually caused by contact
• not every tear needs to be operated on.
• Just take a bit of the meniscus out. Not the whole thing.
• Meniscus is difficult to heal because they don’t have a very good blood supply.

BUT ACL tears are often non-contact related.

Question 38

which knee ligaments can be tested with valgus and varus stress test

Answer 38

collateral ligaments

-MCL– prevents valgus. test using VALGUS stress

LCL– prevents VARUS. test using VARUS stress test.

Question 39

Type of fracture, what type of ligament is compromised?

Answer 39

SEGOND gracture. Bone fragment near the tibia. 99% of the segond fractures also indicate an ACL tear.

Question 40

What’s going on with this knee?

Answer 40

Younger person. Can see growth plates. There’s a little chunk of bone sticking up on the lateral side of the knee. Instead of the ACL ligament tearing itself,it tears a piece of bone from it’s attachment— called an evulsion.

Might be able to put bone back with a screw. If you miss this then they probably are unstable downt he road and Need an ACL reconstruction with 6-9 months of recovery.

Question 41

Which ligament tear of the knee will cause bruisnig? which wont?

Answer 41

MCL and LCL are out of the knee— higher chance of bruising. ACL and PCL are inside the synovial joint in their own wheath and their blood from trauma most likely collects in the synovial joint capsule and doesn’t show bruising.

Question 42

treatment for collateral or cruciate tear

Answer 42

Question 43

Diagnosis?

Answer 43

Dislocated knee. Popliteal artery in posterior position doesn’t have enough stretch in it— if it gets torn, it can get necrosed. YOU MUST REATTACH POPLITEAL ARTERY IMMEDIATELY. They have 6 hours before the muscle starts to die. After that, no recovery.

Question 44

why is a knee dislocation a surgical emergency?

Answer 44

Knee dislocation is a surgical emergency because popliteal artery may be compromised. Need an angiogram. Need to watch for compartment syndrome afterwards too.

Question 45

possible complications after knee dislocation surgery

Answer 45

compartment syndrome. need relief with fasciotomy.