Bone & Joints

Question 1

Name the 4 big categories of diseases of bones & joints.

Answer 1

1. Inflammatory diseases
2. Infections
3. Metabolic bone diseases
4. Neoplasms

Question 2

Name the key inflammatory diseases of bones & joints:

Answer 2

1. Osteoarthritis (degenerative)
2. Rheumatoid arthritis (autoimmune)
3. Crystal arthropathies (crystal deposition, e.g. gout)

Question 3

Types of infections of the bone and joints:

Answer 3

1. Osteomyelitis
2. Chronic osteomyelitis

Question 4

Name the 4 metabolic bone diseases.

Answer 4

1. Osteoporosis
2. Osteomalacia & rickets (Vit D deficiency)
3. Hyperparathyroidism (excess PTH)
4. Paget’s disease (uncoordinated osteoclasts n osteoblast activity)

Question 5

How are neoplasms categorised?

Answer 5

1. Benign or malignant
2. Primary vs metastatic
3. Prognosis of malignant bone tumours
4. Type of tumour (bone forming vs chondroid/cartilage forming)

Question 6

Name the 7 key types of neoplasms.

Answer 6

1. Osteosarcoma (malignant)
2. Ewing sarcoma (malignant)
3. Chondrosarcoma (malignant)
4. Benign chondroid tumours
5. Giant cell tumours (benign)
6. Fibrous tumours (benign)
7. Fibro-osseous tumours (benign)

Question 7

Name the 2 complications of degenerative disc herniation/bulging

Answer 7

1. Myelopathy
   - compresses posteriorly, causing injury to spinal cord
   - aka the upwards one, to the back of spine
2. Radiculopathy
   - compresses postero-laterally, causing injury to nerve roots
   - aka the sideways one

Question 8

Osteoarthritis is..

Answer 8

• the chronic progressive destruction of articular cartilage (aka thinning, erosion & fibrillation ‘cracking;)
• leads to narrowing of joint space
• degenerative in nature, all elderly will get it as they age

Question 9

Rheumatoid arthritis is..

Answer 9

• multi-systemic, chronic inflammatory autoimmune disease affecting many tissues but principally attacking the joints
• commonly involved the small joints (e.g. PIP & MCP joints of the hands, wrists, elbows & knees)

Question 10

Rheumatoid arthritis occurs more commonly in..

Answer 10

More common in
1. Women
2. Small bones/joints
3. Younger pxs

*as compared to osteoarthritis

Question 11

Differences between Osteoarthritis & Rheumatoid arthritis:

Answer 11

Osteo
1. Usually affects larger joints that support a lot of weight
E.g. hips & knees
2. Occurs in older pxs (degenerative nature)

Rheumatoid
1. Usually affects smaller joints
E.g. metacarpal joints in hands
2. Occurs younger pxs (autoimmune nature)

Question 12

Cervical spondylosis spinal nerve compression is due to..

Answer 12

• arthritis occurring in the neck
• special emphasis as it compresses on the spinal nerves

Question 13

Seropositive (rheumatoid) arthritis tells us..

Answer 13

The arthritis is due to presence of several autoantibodies are produced in RA (70-80%)

Impt ones for diagnostic purposes: (via blood test)
1. Rheumatoid factor (RF)
2. Anticitrullinated protein antibody (ACPA)

Question 14

Mechanism of Seropositive Rheumatoid Arthritis? What happens?

Answer 14

• cytokine driven process induces pannus formation
• pannus: specialised granulation tissue that is destructive
• pannus destroys articular cartilage
• scar tissue replaces space, aka fibrosis occurs

Question 15

What is eburnation and thickening of subarticular bone?

Answer 15

Occurs due to degenerative osteoporosis

1. Eburnation: exposed bone
   - bone exposed as smooth polished surface due to constant friction of bone surfaces (cuz cartilage is gone)
2. Formation of subchondral cyst
   - thickening of subarticular bone to compensate for lack of cartilage at area

Question 16

What is Paget’s disease?

Answer 16

• Uncontrolled, excess bone resorption + uncoordinated osteoblastic response (bone formation)
• results in: rapid turnover of ‘poorly made’ bone
• more common in elderly

Question 17

Gout is characterized by..

Answer 17

• increased serum uric acid and urate crystals deposition

Question 18

Causes of Gout..

Answer 18

Primary or Secondary

Primary
- gout is mostly primary
- idiopathic
- associated w obesity, alcohol, hypertension & fatty diet

Secondary
- due to known conditions that promote hyperuricemia
- e.g. specific drugs, renal failure, familial juvenile hyperuricaemic nephropathy & congenital enzyme defects

Question 19

Long term complications of gout if not treated?

Answer 19

• deposition of crystals => forms deformities
• can cause kidney failure

Notes:
- deformities
- erosion of joints
- kidney disease (stones)
- renal failure

Question 20

Diagnosis of Gout via..

Answer 20

Examination of synovial fluid using Polarized light under microscope

• key point: not normal light microscope! (common exam qns)

Question 21

Name the 2 shapes of Calcium pyrophosphate crystals.

Answer 21

Examination under polarized light reveals

1. Strongly birefringent, needle shaped crystals
   => Gout
2. Weakly birefringent, rhomboid-shaped crystals
   => Pseudogout

Question 22

What is Sequestrum?

Answer 22

Native necrotic bone causing deformities
- that has become separated from normal/sound bone during the process of necrosis
- complication of osteomyelitis

Question 23

What is involucrum?

Answer 23

Sleeve of reactive woven bone tissue
- secreted by periosteum
- periosteum continues laying down bone in the pocket below even though bone is dead

Question 24

What is Tuberculous osteomyelitis?

Answer 24

• extrapulmonary tuberculosis via hematogenous dissemination (blood borne/lymphatic drainage)
• specific type of chronic osteomyelitis
• highly destructive w extensive necrosis, difficult to treat

Question 25

What is Osteoporosis?

Answer 25

- issa **diagnosis** - characterised by **reduced bone mass**, leading to fragility & susceptibility to fractures - no defined cause as it is simply a diagnosis

Question 26

What are some causes of Osteoporosis?

Answer 26

Commonly 1. Primary/idiopathic - due to postmenopausal condition in older females, due to **estrogen deficiency** - or idiopathic (no known cause) 2. Secondary (less common) - endocrine - GIT disturbance (malnutrition, reduced Ca intake) - drugs (corticosteroids, chemotherapy - immobilisation

Question 27

What is Osteomalacia?

Answer 27

Osteomalacia: **defect in matrix mineralisation (calcification)** due to **abnormal VitD metabolism or deficiency** <= clear cause unlike in osteoporosis

Question 28

What is the difference btw Rickets and Osteomalacia?

Answer 28

1. Rickets - in children => that are **still developing** - lack of calcium => inability to form bone - developing bone remains as cartilage => easily bendable - presents as bone deformities & microfractures 2. Osteomalacia - in adults - bones are alr fully developed - thus, osteomalacia only presents as microfractures, no bending

Question 29

Manifestations/symptoms of Rickets are..

Answer 29

1. **Severe bowing of leg** 2. Bossing: distortion of skull 3. **Rachitic Rosary**: when rib cartilage undergoes hypertrophy but no calcification, so ribs appear **enlarged w beadlike prominences** Due to: - disturbance of endochondral ossification => **overgrowth of epiphyseal cartilage** => failure of cartilage cells to mature

Question 30

What is Osteitis Fibrosa Cystica?

Answer 30

Osteitis Fibrosa Cystica: **excessive osteoclastic activity due to hyperparathyroidism** => leads to hypercalcaemia & low level serum phosphate => loss of bone mass due to bone resorption (osteoclastic giant cells removing bone) => lytic lesion => fibrous tissue replaces bone (peritrabecular fibrosis)

Question 31

What is Brown Tumour?

Answer 31

- ‘tumoral’ form of osteitis fibrosa cystica - composed of accumulation/solid mass of osteoclastic multinucleated giant cells