8 - Disorders of the Knee

Question 1

What are the best ways to x-ray image the knee?

Answer 1

Question 2

When do femoral shaft injuries occur?

Answer 2

• High velocity trauma e.g RTA
• Child abuse
• Osteoporotic or bone lesions can lead to fractures with low velocity e.g falling over from standing

Question 3

Who is at risk of getting knee disorders?

Answer 3

• Elderly
• Obese people
• Athletes

Question 4

What is the danger of femoral shaft injuries?

Answer 4

• Hypovolaemic shock due to blood loss of around 1-1//5 litres in closed fracture, can be double this in open fracture
• Fix surgically

Question 5

How does a femoral shaft get deformed after fracture and why?

Answer 5

- Proximal part usually abducted due to glut med and min on greater trochanter

• Proximal flexed due to iliopsoas on lesser trochanter
• Distal adducted into varus deformity due to adductor muscles and extended due to gastrocnemius on posterior femur

Question 6

What is a distal femoral fracture, who is at risk and what is the major risk with this type of fracture?

Answer 6

• Young people in high energy sporting injury or old person with osteoporotic bone and a fall

- Popliteal artery can become involved so have to assess status of limb before and after reduction of fracture

https://chestofbooks.com/health/anatomy/Human-Body-Construction/Fractures-Of-The-Femur-Continued.html

Question 7

What do tibial plateau fractures look like?

Answer 7

• Due to high energy injuries of axial loading with valgus or varus angulation of knee
• Uni/Bicondylar (mainly lateral tibial condyle)
• Articular cartilage always damage so fracture fragments have to be removed but almost always get OA after surgery
• These fractures associated with ACL injuries and meninscal tears

Question 8

What are the causes of a patella fracture, what are the two types and how are they treated?

Answer 8

• Direct impact injury (e.g dashboard) or eccentric contraction of quadriceps (e.g skiing)

Displaced:

• Reduce and fix

Undisplaced:

• Splint and protect e.g crutches

Question 9

How can you tell when examining a patient that they may have a patellar fracture?

Answer 9

- Palpable defect in patella

- Haemarthrosis in joint

- Extensor mechanism may be disrupted if fracture splits patella distal to insertion of quadriceps tendon (displaced fracture)

Question 10

Why may a patient appear to have a patellar fracture but they haven’t had any trauma?

Answer 10

• Bipartite patella
• Failure of union via ossification so fibrocartilage remains

Question 11

What is the difference between patella dislocaiton and subluxation?

Answer 11

• Dislocation is when patella is completely displaced from normal alignment
• Subluxation is partial displacement

Question 12

What is the most common way for the patella to dislocate, why, and how does the anatomy of the knee try to avoid this?

Answer 12

- Laterally

• Q angle between pull of quad tendon and patellar ligament means most likely to go laterally
• Usually VMO contraction stabilises patella in trochlear groove and controls tracking of patella

Question 13

What movement is most likely to cause patellar dislocation and who is predisposed to these injuries?

Answer 13

• Twisting injury in slight flexion or direct blow to knee
• Mainly sporty teenagers with internal rotation of femur on planted foot whilst flexing knee

Who?

• Generalised ligamentous laxity
• Weakness of quad muscles, e.g VMO
• Shallosw trochlear groove with flat lateral lip
• Long patellar ligament
• Previous dislocations

Question 14

How do you treat a patella dislocation?

Answer 14

• Extending knee and manually reducing patella
• Immobilisation during healing
• Physiotherapy to strengthen VMO

Question 15

When do meniscal tears occur and what do they look like on MRI?

Answer 15

• Sudden twisting motion of weight bearing knee in high degree of flexion
• May be some knee joint effusion too due to fluid and fluid in area of tear (white)

Question 16

What are the two types of meniscal tear and how are meniscal tears treated?

Answer 16

• Acute usually surgical meniscetomy or meniscal repair
• Degenerative usually rehabilitation and conservative as surgical not long prognosis

Question 17

What will the patient normally present with with a meniscal tear?

Answer 17

• Intermittent pain localised to joint line
• Knee clicking, catching and locking
• Giving way sensation
• Swelling may be delayed symptom due to reactive effusion

Question 18

What does locking of the knee mean when a patient describes it?

Answer 18

Inability to full extend knee due to intra-articular foreign body

Question 19

What things affect the knee stability?

Answer 19

- Static: bones and ligaments

- Dynamic: muscles and tendons

Question 20

What is the unhappy triad?

Answer 20

• Three tears due to a strong force applied to the lateral aspect of the knee
• Medial meniscus is adherent to medial collateral ligament which is why it tears too

Question 21

What is the role of the collateral ligaments and how are they injured?

Answer 21

• Control lateral movement of knee joint and brace against unusual angulation
• Also, work with PCL to prevent excessive posterior motion of tibia on femur.
• Injured due to acute varus or valgus angulation of knee

Question 22

What will patients present with when they have a collateral ligament injury?

Answer 22

• Pain and swelling of knee immediately
• Joint unstable and patient complains of giving way or not supporting body weight
• Brace and rehab or surgery with unhappy triad

Question 23

What collateral ligament breaks with each strain?

Answer 23

- Valgus: medial at risk (more common)

- Varus: lateral at risk

• LCL break will cause more knee instability as shallower socket for femoral condyle on lateral side

Question 24

What does the ACL normally do and how is it torn?

Answer 24

• Controls rotational stability of the knee
• More common tear than PCL
• Quick deceleration, hyperextension or rotational injury (sudden change in direction) can cause tear
• Usually non contact injury
• Can be torn by large force to back of knee in slight flexion

Question 25

What does an ACL tear normally present as and how is it fixed?

Answer 25

- Popping sensation with immediate swelling - Instability of knee due to tibia sliding anteriorly 'giving way' **Treat:** - Low functional demand on knee can use musculature to stabilise joint - Sportsman need surgical reconstruction

Question 26

How does PCL tear occur?

Answer 26

- Dashboard injury as knee is flexed and large force applied to upper tibia displacing it posteriorly - Person falling on flexed knee with ankle plantarflexed - Tackle with knee flexed - Severe hyperextension can avulse PCL from it's insertion

Question 27

What tests can be done to check the stability of the cruciate ligaments?

Answer 27

- Lachman's Test (ACL) - Anterior and Posterior Drawer tests

Question 28

How do you dislocate the knee, what are the complications and how do you treat it?

Answer 28

- Uncommon and due to high energy as have to rupture 3 out of 4 ligaments - Popliteal artery injury as tethered proximally. Can lead to haematoma, be crushed or traction injury leading to thrombotic occlusion - Reduce and stabilise and then test vasculature with MRA

Question 29

What are some of the causes of swelling around the knee?

Answer 29

**- Bony:** Osgood-Schlatter's **- Soft tissue**: localised popliteal lymph node or artery. generalised lymphoedema **- Fluid:** effusion in joint or soft tissue haematoma outside

Question 30

What are the two main types of knee effusions?

Answer 30

**Acute:** \<6 hours after injury due to haemarthrosis **Delayed:** \>6hours after injury due to reactive synovitis, inflammation of synovium so more synovial fluid NEVER NORMAL

Question 31

What are the two types of acute knee effusion and what do they indicate?

Answer 31

**- Haemoarthrosis:** blood in joint **- Lipo-haemarthrosis:** blood and fat in joint due to release from bone marrow

Question 32

What is pre-patellar bursitis?

Answer 32

**- Housmaid's knee** - Knee pain and swelling with redness overlying inflammed bursa - Patient cannot walk or kneel due to pain - History of repetitive trauma or may be history of blunt trauma to knee up to 10 days after incident

Question 33

What is infrapatellar bursistis?

Answer 33

**- Clergyman's knee** **-** Mostly affects superficial infrapatellar bursa - Repetitive microtraume by activities involving kneeling

Question 34

What is suprapatellar bursitis?

Answer 34

- This bursa is extension of synovial cavity so knee effusion usualy presents with swelling in this pouch - Shows got a swelling in knee joint

Question 35

What is semimembranosus bursitis?

Answer 35

- Indirect consequence of swelling in knee joint - Attached to posterior capsule of knee joint beneath deep fascia of popliteal fascia - If effusion in knee joint, fluid can force way out of small opening into semimembranosus bursa **- Popliteal cyst or Baker's cyst**

Question 36

What is Osgood-Schlatter's Disease (OSD)?

Answer 36

**- Inflammation of apophysis (insertion) of the patellar ligament onto tibial tuberosity** - In sporty teenagers and can cause localised pain and swelling - Bilateral 20-30% cases - Intense knee pain during running, jumping, squatting, climbing stairs and kneeling - Resolves with rest and ice. Pain and swelling resolve at age of skeletal maturity as apophysis fuses but bony prominence remains

Question 37

What are the typical symptoms of knee OA?

Answer 37

**- Knee pain, stiffness and swelling** - Knee pain comes and goes, precipitated by activities, pain and stifness after prolonged inactivity - Valgus, varus or fixed flexion deformity - Crepitus - Effusion - Buckling knee (quad muscle weakness and instability of knee) - Uni, bi or tricompartmental

Question 38

What are some risk factors for knee osteoarthritis?

Answer 38

- Female - Age - Obesity - Trauma to joint - Another condition affecting joint - Family history

Question 39

What is the initial treatment for knee OA?

Answer 39

- Strengthen vastus medialis muscle to reduce instability - Weight loss - Analgesia - Activity modification - Finally total knee replacement

Question 40

What is the best way to image for osteoarthritis of the knee?

Answer 40

Weightbearing so can see if bicompartmental etc

Question 41

What is septic arthritis?

Answer 41

- Most common knee, hip, shoulder, ankle wrists - Most common is Staph aureus. Can be staph.epidermidis, neisseria gonnorhoeae, step.viridans, strep,pneumoniae and Group B streptococci - Bacteria damage articular cartilage directly, e.g proteases from Staph.aureus, or stimulate neutrophils to hydrolyside collagen and proteoglycans

Question 42

What are risk factors for septic arthritis?

Answer 42

- Age - Immunosuppression - Diabetes mellitus - IV drug use - Prosthetic joints (intraoperative or haematogenous spread) - Delayed wound healing - Polymethacrylat cement inhibite WBC and complement function

Question 43

What do patients with septic arthritis usually present with?

Answer 43

**- Symptom triad:** Fever, Pain, Reduced range of motion developing over few days or weeks - Erythema, swelling, warmth, tenderness, limited range of movement - In prosthetics not much swelling or symptoms but may find draining sinus from underlying infected joint

Question 44

What should you do if you suspect septic arthritis?

Answer 44

- Immediate aspiration of joint and aspiratie sent for urgent culture - Surgical washout and antibiotics (most people have decreased range of motion and chronic pain if resolved and don't die)

Question 45

Why do some patients with osteoarthritis of the knee describe their knee giving way or buckling?

Answer 45

Patients with a painful stiff knee tend to move the joint less (to avoid pain) and therefore develop muscle weakness, especially of the quadriceps muscles, leading to instability of the joint. Quadriceps weakness manifests as reduced power of knee extension, and therefore the patient experiences sudden flexion ('giving way') of their knee.