Clinical Conditions of the Hip Joint

Question 1

How is Osteoarthritis defined pathologically?

Answer 1

A degenerative disorder arising from the breakdown of articular hyaline cartilage

Question 2

How is Osteoarthritis defined clinically?

Answer 2

A clinical syndrome comprising joint pain accompanied by functional limitation and reduced quality of life

Question 3

What is Osteoarthritis?

Answer 3

It’s a chronic disease of the musculoskeletal system without systemic involvement (i.e. no involvement of eyes, skin, etc) and is non-inflammatory.

Question 4

Is ankylosis seen in Osteoarthritis?

Answer 4

Compared with some inflammatory arthropathies (e.g. ankylosing spondylitis), ankylosis (bony fusion across a joint) is very rarely seen in osteoarthritis.

Question 5

How can OA be classified?

Answer 5

OA can be classified into primary or secondary
Primary OA - cause is unknown
Secondary OA - cause is known

Question 6

Give examples of causes of secondary OA

Answer 6

Trauma, Metabolic disorders affecting the joint (e.g. gout), Inflammatory arthritis (e.g. rheumatoid arthritis)

Question 7

What are the risk factors for OA?

Answer 7

Obesity, Age, Female sex

Question 8

What are the symptoms of OA?

Answer 8

Deep aching joint pain, exacerbated by use
Reduced range of motion and crepitus (grinding)
Stiffness during rest (morning stiffness, usually lasting <1 hour)

Question 9

Describe the pathology of osteoarthritis

Answer 9

Hyaline cartilage covering the articular surface becomes swollen due to increased proteoglycan synthesis by chondrocytes, with increased numbers of chondrocytes differentiating from chondroprogenitor cells. This is due to an attempt to repair the cartilage damage and can last for several years
As the disease progresses, however, the level of proteoglycans falls, causing the cartilage to soften and lose elasticity. Microscopically, flaking and fibrillations (vertical clefts) develop along the normally smooth articular surface. Over time, the cartilage becomes eroded down to the subchondral bone, resulting in loss of joint space. These surface changes in the cartilage alter the distribution of biomechanical forces and trigger further active changes in the tissues. The subchondral bone responds with vascular invasion and increased cellularity, becoming thickened and dense at areas of pressure. This is eburnation, and manifests as subchondral sclerosis on X-rays.
The traumatised subchondral bone may also undergo cystic degeneration to form subchondral cysts. These are attributable to either osseous necrosis secondary to pressure, or to the intrusion of synovial fluid.
At areas along the articular margin, osseous metaplasia of connective tissue occurs, leading to irregular outgrowth of new bone (osteophytes)

Question 10

Name the four cardinal signs of OA on an X-ray

Answer 10

Reduced joint space
Subchondral sclerosis
Bone cysts
Osteophytes

Question 11

If a patient experiences osteoarthritis of the hip, why might they feel pain radiating to the knee?

Answer 11

Pain is radiated to the knee via the obturator nerve

Question 12

What is the cure for osteoarthritis of the hip?

Answer 12

Total Hip Replacement

Question 13

Define a fractured neck of femur

Answer 13

A fracture of the proximal femur, up to 5cm below the greater trochanter

Question 14

What are the symptoms of a fracture neck of femur?

Answer 14

Reduced mobility/sudden inability to bear weight on the limb
Pain which may be felt in the hip, groin and/or knee

Question 15

How does a fractured neck of femur present on examination?

Answer 15

The affected leg is shortened, abducted and externally rotated.

Question 16

What else can be seen on examination of a fractured neck of femur?

Answer 16

There is exacerbation of pain on palpation of the greater trochanter and pain is exacerbated by rotation of the hip. When examining a fractured hip, avoid vigorous examination as there’s a risk of displacing the fracture

Question 17

How can a fractured neck of femur be classified?

Answer 17

Intracapsular - either subcapital or transcervical

Extracapsular - either intertrochanteric or subtrochanteric See pic

Question 18

Why are intracapsular fractures more problematic?

Answer 18

Intracapsular fractures are likely to disrupt the ascending cervical branches of the medial femoral circumflex artery. Due to the inability of the artery in the ligament to the head of femur to sustain the metabolic demand of the femoral head, there’s a high risk of avascular necrosis of the bone. The risk is increased if the fracture is displaced

Question 19

Why are extra capsular fractures less problematic?

Answer 19

The ascending cervical branches of the MFCA to the femoral head is likely to remain intact

Question 20

Why is the limb shortened, abducted and externally rotated in a displaced fractured neck of femur?

Answer 20

Shortened - strong muscles of the thigh (flexors, adductors and extensors) pull the distal fragment of the femur upwards
Externally rotated - the fractured neck of femur allows the shaft of the femur to move independently of the hip joint; the axis of rotation of the femur that normally passes through the head shifts to pass through the greater trochanter and along the long axis of the femoral shaft. The iliopsoas now acts as an external rotator of the femur because of the fractured neck
Abducted - the strong abductors that attach to the greater trochanter abduct the femur distal to the fracture site

Question 21

In which direction are most hip dislocations?

Answer 21

Most hip dislocations are posterior. The most common cause is the knee impacting the dashboard during a road traffic collision..

Question 22

What position will the affected limb of a posterior hip dislocation be in?

Answer 22

The affected limb will be in a position of flexion, adduction and internal rotation.
A sciatic nerve palsy is present in some cases

Question 23

What position will the affected limb of an anterior hip dislocation be in?

Answer 23

The affected limb is held in a position of external rotation with mild flexion and abduction.
Femoral nerve palsies can be present but are uncommon.

Question 24

Why does shortening and internal rotation of the limb occur after posterior dislocation of the hip?

Answer 24

Shortening - the femoral head is pushed backwards over the posterior margin of the acetabulum and comes to lie on the lateral surface of the ilium. The head of the femur is then pulled upwards by the strong extensors (gluteus maximus and hamstrings) and adductors of the hip, causing limb shortening
Internally rotated - the anterior parts of the gluteus medius and minimus pull on the posteriorly-displaced greater trochanter and cause the femur to rotate internally.

Question 25

What does the superior gluteal nerve supply?

Answer 25

The superior gluteal nerve supplies the abductors of the hip: gluteus medius and gluteus minimus.

Question 26

What happens in a superior gluteal nerve lesion?

Answer 26

Weakness in abducting the thigh at the hip

Question 27

What happens when a healthy standing person is asked to lift one foot off of the ground?

Answer 27

The gluteus medius and minimus of the supporting limb usually contract, preventing the tipping of the pelvis towards the unsupported side

Question 28

What happens when a person with superior gluteal nerve palsy is asked to stand on their injured lower limb?

Answer 28

The pelvis on the unsupported side descends. This is Trendelenburg sign

Question 29

What other causes of Trendelenburg sign are there?

Answer 29

Fracture of the greater trochanter (site of insertion of the gluteus medius)
Dislocation of the hip joint