Lower Limb Arthritis Flashcards
What is gout?
Inflammatory arthritis, arising from hyperuricemia and deposition of monosodium urate crystals in the joints
What causes hyperuricemia?
- Excess purines (high purine diet, enzymatic defects)
- Increased catabolism of nucleic acids due to high cell turnover (infections, cancer)
- Decreased renal excretion of uric acid
What are risk factors for gout?
- Male
- Old
- Diabetes, Hyperlipidemia, Hypertension
- Hyperuricemia-inducing drugs (thiazide/loop diuretics, ciclosporin, aspirin)
What is the pathophysiology of gouty arthritis?
- Hyperuricemia > precipitation of MSU crystals in bloodstream > deposition in joints and surrounding tissues
- Causes inflammation, releasing IL-1 to recruit neutrophils
- Neutrophils release inflammatory mediators to attract other phagocytes, and attempt to phagocytose crystals
- Phagocytes’ lysosome membranes are damaged by crystals, releasing hydrolytic enzyme content
- Manifests as severe, sudden inflammatory attack, esp. at MTP of big toe
- Over time, recurrent crystal deposition can cause firm yellow nodules (tophi) around joints and ears
S/S of gout?
- Needle-like crystals in joint aspirate
- Sudden, severe inflammatory arthritis attacks (esp. at night)
- Limited ROM due to pain
- Tophi
- Advanced, LT gout can cause joint destruction + hypertrophy (bony sclerosis), leading to overhanging edges in the joint
Treatment of gout?
Uric acid-lowering therapies
Who are uric acid-lowering therapies indicated for?
- > 65 y/o
- CKD
- > 5 gouty attacks / year
- Tophi
What is pseudogout?
Gout-like inflammatory arthritis, arising from deposition of calcium pyrophosphate dihydrate crystals in the joints. aka Chondrocalcinosis
What causes pseudogout?
Idiopathic; associated with trauma, hyperparathyroidism, and haemochromatosis
S/S of pseudogout?
- Usually asymptomatic, or similar to gout
- Under polarised light, joint aspirate reveals strongly birefringent, rhomboid-shaped crystals
How to differentiate between gout and pseudogout?
Joint aspirate crystals
What is septic arthritis?
Suppurative inflammatory arthritis, caused by infectious agent
What usually causes septic arthritis?
- Streps, S. aureus, Pseudomonas, GN rods (e.g. Gonococcus)
- Spread via blood; direct inoculation; spread from adjacent soft tissue infections / osteomyelitis
S/S of septic arthritis?
- Red, hot, swollen joint
- Rapid onset joint pain, worsened with movement
- Purulent fluid in joint aspirate
- Unilateral hip / knee joints affected
Unique S/S of gonococcal septic arthritis?
- Septic emboli
- STD / UTI symptoms, e.g. painful micturition
- GN rods in joint aspirate
Describe treatment of gonococcal septic arthritis.
IV/IM ceftriaxone
Unique S/S of S. agalactiae septic arthritis?
- Gp B Streps in joint aspirate
- Associated with raw fish consumption
What is osteomyelitis?
Bone infection involving cortex, medulla, and periosteum, usually caused by S. aureus
What usually causes osteomyelitis?
- S. aureus
- Spread via blood, direct inoculation, or from adjacent soft tissue infections
How do you detect osteomyelitis?
- MRI
- Tissue culture / Biopsy
How do you treat osteomyelitis?
Targeted, specific antibiotic therapy
What is suppurative osteomyelitis?
Acute / Acute-on-chronic pyogenic osteomyelitis
What is the pathogenesis of suppurative osteomyelitis?
- Infection localised in cortex, forming small abscess
- Abscess enlarges, and grows into sub-periosteal space
- Abscess may escape from bone via sinus tracts
- Abscess may undergo necrosis
What are the possible sequelae of suppurative osteomyelitis?
- Healing and resolution
- Subacute / Chronic suppurative osteomyelitis
- Abscess, necrosis
- Pathological fractures / deformities (proliferative periostitis, involucrum)
- Sinus tract formation in skin and soft tissue
- Secondary amyloidosis
- Malignant transformation to osteosarcoma (bone) / squamous cell carcinoma (sinus tract)
What is proliferative periostitis?
- Extensive new bone formation, especially in children’s jaws (Garre’s sclerosing osteomyelitis)
- Causes irritation, trauma, and dental infection
What is involucrum?
Sleeve of reactive woven bone tissue around necrotic native bone
Which bones are commonly affected in children for osteomyelitis?
Long bones, jaw
Which bones are commonly affected in adults for osteomyelitis?
Small bones of foot, femur, spine
How do suppurative and chronic osteomyelitis differ?
- Mainly chronic inflammatory infiltrate and fibrosis, with little pus
- Sclerosis, proliferative periostitis
Why can chronic osteomyelitis occur?
- Delayed diagnosis
- Inadequate treatment (antibiotics, surgical debridement of necrotic bone)
- Immunocompromised
What are the possible sequelae of chronic osteomyelitis?
- Pathological fractures / deformities
- Secondary amyloidosis
- Malignant transformation to osteosarcoma (bone) / squamous cell carcinoma (sinus tract)
- Spread of infection
What is tuberculous osteomyelitis?
A subtype of chronic osteomyelitis, caused by TB
How does tuberculous osteomyelitis spread?
Via blood / lymph
Who is more at risk of tuberculous osteomyelitis?
Immunocompromised patients
Why is tuberculous osteomyelitis hard to treat?
Extensive necrosis, highly-destructive
S/S of tuberculous osteomyelitis?
- Greater spinal involvement, causing compression fractures, deformities (scoliosis/kyphosis), and neurological deficits from spinal cord/nerve damage
- Chronic inflammatory infiltrate
- Epithelioid granulomas with caseating necrosis
What is osteoarthritis?
- Degenerative inflammatory joint disease
What are the three types of osteoarthritis?
- Primary generalised OA (usually affects post-menopausal women)
- Erosive inflammatory OA (rapid, severely damaging)
- Hypertrophic OA (florid osteophyte formation, slowly-progressing bony sclerosis)
What is the pathophysiology of osteoarthritis?
- Wear and tear causes degeneration of articular cartilage
- Subchondral bone exposed; osteophytes attempt to repair damage, leading to bony spur formation (further restricts movement)
- Mild synovial inflammation from articular cartilage breakdown also occurs
S/S of osteoarthritis?
- Hips and knee joints affected more
- Joint pain (worsened on exertion)
- Mild inflammation, incl. morning stiffness
- Crepitus
- Bony erosion (eburnation, where surface is polished smooth; subchondral cyst)
- Bony spurs, sclerosis (may cause spinal nerve compression)
- Joint deformities (Heberden (dorsal PIPJ) and Bouchard (DIPJ) nodes)
- Joint space narrowing (fibrillation, thinning, erosion)
How is osteoarthritis detected?
X-rays
What is the pathophysiology of degenerative intervertebral disc?
- Nucleus pulposus loses matrix’s water content, thus reducing its shock-absorbing capability
- Fibrous disc annulus becomes brittle and prone to tearing due to repeat microtrauma
- Disc herniation may occur, where the nucleus pulposus prolapses out of the disc annulus
What are causes of degenerative intervertebral disc?
- Wear and tear
- Mechanical factors (posture, trauma)
- Genetics
- Others (nutrition, metabolism, infection)
What are complications of disc herniation from degenerative intervertebral disc?
- Posterior prolapse compresses spinal cord
- Posterolateral prolapse compresses spinal nerve roots
What is rheumatoid arthritis?
Autoimmune attack of citrullinated proteins in the synovial membrane, leading to inflammation and thickening
What are risk factors for rheumatoid arthritis?
- Female
- HLA-DRB1 gene
Pathophysiology of rheumatoid arthritis?
- autoAbs target citrullinated proteins, which are mostly found in joints
- leads to synovial membrane inflammation and thickening, and a pannus may be created to invade the articular cartilage and erode the underlying bone
- ankylosis (abnormal fusion) may occur
S/S of rheumatoid arthritis?
- Inflammatory joint pain w/ morning stiffness
- Deformities (swan neck deformity, Boutonniere’s deformity, rheumatic nodules, ankylosis)
What is swan neck deformity?
- Hyperextended PIPJ, flexed DIPJ
- Due to imbalance between extensor and flexor tendons (from chronic synovitis)
What is Boutonniere’s deformity?
- Flexed PIPJ, hyperextended DIPJ
– Due to imbalance between extensor and flexor tendons (from chronic synovitis)
What are rheumatic nodules?
- Granulomas with a zone of central necrosis, which manifest as firm subcutaneous nodules
- Due to immune complex deposition
What joints are usually affected first in rheumatoid arthritis?
Small joints of the hand
What Ab are used to detect rheumatoid arthritis?
- ACPA / anti-CCP Ab
- RF
What is systemic lupus erythematosus?
An autoimmune disease, characterised by immune complex deposition and inflammation in many tissues
S/S of SLE?
- Butterfly-shaped malar rash
- Discoid lupus rash
- Photosensitivity rash
- Livedo reticularis rash
- Alopecia
- Oral ulcers
- Polyarthritis of small joints, with no significant erosion
- Lupus nephritis (glomerulonephritis)
- Autoimmune haemolytic anaemia
- Serositis
What is Sjögren’s syndrome?
- Autoimmune attack on exocrine glands, esp. salivary and lacrimal glands.
- Associated with attack on joints
Pathophysiology of Sjögren’s syndrome?
- AutoAbs (anti-RO and anti-LA) attack exocrine glands
- Lymphocytic infiltration also occurs
- This leads to swelling and fibrosis of the glands, esp. the parotid gland
- Non-erosive arthritis also occurs
S/S of Sjögren’s syndrome?
- Usually asymptomatic until dryness is severe
- Dry, painful eyes > ocular lesions, blurry vision
- Xerostomia > dental caries, difficulty swallowing
How do we detect Sjögren’s syndrome?
- Salivary gland biopsy to detect lymphocytic cell infiltrate
- Schirmer’s test, where absorbent strip of paper is placed under lower eyelid to measure tear production
What is psoriatic arthritis?
Autoimmune attack of skin and joints; commonly affects joints, tendons, and entheses
Pathophysiology of psoriatic arthritis?
- Idiopathic
1. Inflammation starts at entheses, and gradually leads to bone erosion (pannus) and hypertrophy (bony spurs, ankylosis)
S/S of psoriatic arthritis?
- Dactylitis - red, hot, swollen (sausage-like) digits
- Enthesitis - pain and tenderness, esp. Achilles’ tendon
- Asymmetrical arthritis, esp. hands and feet
- Nail changes - oncholysis, pitting, hyperkeratosis
- Psoriatic plaques, esp. elbows, knees, and scalp
- Arthritis mutilans - rare deformity of fingers and toes due to severe inflammation
- Spinal disease - rare
How do we detect psoriatic arthritis?
Imaging for pencil-in-cup deformity, where distal bone’s end is eroded into sharp tip, and proximal bone’s end is hypertrophic and concave
