4.1 The Knee disorders

Question 1

How do femoral shaft fractures occour?

Answer 1

High velocity trauma

Elderly with osteoporotic bone or bone metastasis or other bone lesions e.g bony cysts, fracture can occur from low velocity injury.

In children consider child abuse

Question 2

What happens to the proximal portion of a femoral shaft fracture?

Answer 2

It’s abducted due the pull of the gluteus mediums and minimums on the greater trochanter

It’s also flexed due to the action of iliopsoas on the lesser trochanter

Question 3

What happens to the distal segment on a femoral shaft fracture?

Answer 3

It will be adducted into a varus deformity due to the action of adductor muscles

• adductor Magnus
• gracilis

And extended due to the pull of gastrocnemius on the posterior femur.

Question 4

What will the patient feel in a femoral shaft fracture?

Answer 4

Tense swollen thigh

May have hypovolaemic shock

Question 5

How do distal femoral fractures occur?

Answer 5

Younger = high energy sporting injury 
Elderly = osteoporotic bone, fall from standing

Question 6

What artery may be involved in a distal femoral fracture?

Answer 6

Popliteal artery may be involved if there’s significant displacement of the fracture

Question 7

How can you tell from an x ray that you’re looking at a child?

Answer 7

Infused epiphyses

Question 8

What will you see upon examination of a patella injury?

Answer 8

Palpable defect in patella and joint will be swollen due to blood (haemathrosis)

The patient will be unable to perform a straight leg raise

Question 9

What is the most common direction for patella dislocation and how does it occour?

Answer 9

Mostly laterally dislocations

Due to TRAUMA
Occurs in athletes who may suddenly change direction running during sports

Question 10

How is the patella kept in place?

Answer 10

The vastus medallus obliquus (VMO) which is an inferior horizontal fibre of the vastus medialis

Stabilised the patella within the patella groove

Question 11

How can you be predisposed to a patellar dislocation?

Answer 11

• weakness of quadriceps muscles, especially VMO
• shallow patella groove in femur
• patellofemoral joint hypermobility or maltracking

Question 12

Why do meniscal injuries occur and what will you observe upon examination?

Answer 12

Occur due to a sudden twisting motion of the weight bearing knee

Patient usually has joint line tenderness and restricted motion due to pain or swelling

Swelling is usually delayed/absent as menisci are avascular expect periphery. So, if swollen, due to tear in periphery or an associated injury to the anterior crucial ligament.

Question 13

What is a chronic effusion and how is it linked to synovitis?

Answer 13

Chronic effusion = increased synovial fluid
Synovitis = inflammation of synovial membranes

Chronic effusion can occur due to synovitis

Question 14

What is the difference between varus and valgus deformation?

Answer 14

Varus = medial angulation of distal segment
Valgus = lateral angulation of distal segment

Remember vaLgus = Lateral

Question 15

What ligaments control varus of valgus deformation in the knee joint?

Answer 15

Medial and lateral collateral ligaments keep knee in place

Posterior cruciate ligament chimes in to prevent excessive posterior motion of the tibia on the femur

Question 16

What ligament is more to injury and which is worse if torn, the medial collateral ligament or the lateral collateral ligament?

Answer 16

Medial collateral ligament = more prone to injury

Lateral collateral ligament = worse if injured. This is because the medial tibial plateau forms a deeper and more stable socket with the femoral condyle than the lateral plateau.

Question 17

What’s the unhappy triad?

Answer 17

Injury to

• anterior cruciate ligament
• medial collateral ligament
• medial meniscus

Results from a strong force applied to the lateral aspect of the knee.

Question 18

Where to the anterior and posterior cruciate ligament extend from?

Answer 18

Extend from the intercondylar eminence of the tibia to the intercondylar notch of the distal femur

ACL attaches to posterior aspect of femoral notch and the anterior intercondylar region of the tibia.

PCL goes from medial edge of lateral femoral condyle and the roof of the intercondylar notch. It stretches posterolaterally towards to posterior surface of the tibia.

Question 19

What do the ACL and PCL do?

Answer 19

ACL resists anterior translation and medial rotation of the tibia in relation to the femur

PCL prevents posterior dislocation of the tibia on the femur

Question 20

How is the ACL usually torn and what does the patient feel?

Answer 20

As a result of quick deceleration, hyperextension or rotational injury
The tibia can slide anteriorly under the femur
Usually feel a popping sensation in the knee.

Question 21

How is the PCL damaged?

Answer 21

Dashboard injury = flexion of the knee and a force placed on the upper tibia, displacing it posteriorly

Also during football when a player falls on a flexed knee when their ankle plantar flexed

Question 22

What’s prepatella bursitis and how will patients present?

Answer 22

Inflammation of the prepatella bursa. A superficial bursa between the skin and patella.

Inflammation causes increase in fluid.
Patient has pain and swelling, cant kneel on affected knee and cant walk due to pain.
Usually a history of repetitive trauma to the bursa e.g kneeling on the ground to scrub = housemaids knee.

Question 23

What is infrapatella bursitis and how does it occur?

Answer 23

Two bursa - one below the knee cap and one deep between the patella tendon and tibial bone (shin).

Usually superficial one is inflammed

Occurs due to repeated micro trauma e.g repeated kneeling. Clergymans knee = common nickname and reflects upright position of kneeling.

Question 24

What’s suprapatella bursitis

Answer 24

Swelling within the suprapatellar pouch presents with a knee effusion.

It’s usually a sign of pathology in the knee. Causes can be osteoarthritis or rheumatoid arthritis, gout, infection, repetitive microtrauma, ect.

Question 25

What’s osgood schlatters disease and what do patients complain of?

Answer 25

Inflammation of the patellar ligament at its insertion into the tibial tuberosity. Commonly occours in teenagers who play sport.

Complain of intense knee pain during running, jumping, squatting, ascending and descending stairs and during kneeling.
Resolves with rest and ice.

Question 26

What are the symptoms of osteoarthritis in the knee?

Answer 26

Pain comes and goes at varying levels of intensity
Pain precipitated by activities e.g bending, kneeling, squatting or climbing stairs
Pain is worse after prolonged inactivity or rest e.g getting out of bed in the morning.
Knees may buckle when going downstairs due to weakness of quads causing instability

Loss of articular cartilage = bone rubs on bone = firiction can be felt as crepitus. An effusion may develop.

Question 27

What are the risk factors with OA and what will you see on an X-ray?

Answer 27

Risk factors

• gender (female)
• age
• other conditions effecting the joint
• previous trauma to the joint
• family history

X ray

• osteophytes
• narrow joint space

Question 28

What is septic arthritis of the knee joint and what is the most common cause?

Answer 28

Inflammation caused by the invasion of micro organisms in the joint space

Isn’t sterile unlike reactive arthritis

Common causes

• staphlylococcus aureus
• staph pneumonia
• neiserria gonorrhoea
• group B streptococci
• strep viridans

Question 29

What are the risk factors for septic arthritis?

Answer 29

Age, diabetes mellitus, rheumatoid arthritis, immunosuppressive and IV drug use

Prosthetic joint replacement also. May become symptomatic months or years after initial operation maybe due to delayed wound healing. Biofilm produced by staph epidermis protects bacteria from destruction by antibodies or bodies immune response.

Question 30

What’s the major consequence of septic arthritis?

Answer 30

Damage to articular cartilage due to organisms pathological properties or hosts immune response (neutrophils stimulate cytokines which hydrolyse collagen and proteoglycans).

Question 31

What do patients with septic arthritis present with and what should be done if its suspected?

Answer 31

Present with

• fever
• pain
• reduced range of motion

Also

• red
• swelling
• tender
• warm

If suspected do immediate aspiration of joint and sent to lab for urgent culture.