Lower limb (1) pathologies

Question 1

Describe the pathology of osteoarthritis

Answer 1

1) The hyaline cartilage becomes swollen due to increased proteoglycan synthesis by chondrocytes -> attempt at repairing the cartilage
2) As disease progresses, proteoglycan content falls causing cartilage to soften and lose elasticity
3) Cartilage becomes eroded down to the subchondral bone, resulting in loss of joint space

Question 2

Describe the risk factors for osteoarthritis of the hip and the symptoms described by patients

Answer 2

Risk factors: obesity, trauma, malalignment lead to excessive/uneven loading of the joint
Symptoms: joint stiffness, pain in the hip, reduced mobility, mechanical pain

Question 3

Describe and identify the 4 features of osteoarthritis of the hip on plain X-rays

Answer 3

L = loss of joint space 
O = osteophytes
S = subchondral cysts 
S = subchondral sclerosis

Question 4

Describe the common fractures of the femoral neck

Answer 4

Fractures of the femoral neck = intracapsular & extracapsular (further divided into intertrochanteric and subtrochanteric)
Symptoms = reduced mobility/sudden inability to bear weight on the limb; pain which may be felt in the hip, groin and/or knee

Question 5

Describe the mechanism underlying avascular necrosis of the hip following an intracapsular fracture of the femoral neck

Answer 5

Intracapsular fractures are likely to disrupt the ascending cervical (retinacular) branches of the medial femoral circumflex artery (MFCA)
Due to the inability of the Artery of the Ligamentum Teres to sustain the metabolic demand of the femoral head, there is a high risk of avascular necrosis of the bone

Question 6

Describe the common clinical appearance of the limb after a displaced femoral neck fracture

Answer 6

Affected leg is usually shortened, abducted, and externally rotated
Exacerbation of pain on palpation of the greater trochanter and pain is exacerbated by rotation of the hip

Question 7

Describe the traumatic dislocation of the hip, and the typical clinical appearance

Answer 7

Defined as the head of the femur being fully displaced out of the acetabulum
Dislocations can be traumatic (needs a massive amount of force to dislocate a normal hip) or congenital
Posterior dislocation: affected limb will be shortened, flexed, adducted and medially rotated (sciatic nerve palsy present in some cases)
Anterior dislocation: affected limb externally rotated, abducted with slight flexion (femoral nerve palsy uncommon)
Central dislocation: head of the femur is driven into the pelvis through the acetabulum (palpable on examination)