aspiration

Incidence

Clinically

Unwell / irritable

Fever

Not feeding

Unable to weight bear / limp

Knee pain

Examination

Fever

Limited / painful ROM

Hip held flexed and externally rotated

- maximises volume of capsule

Lab tests

WCC > 12 000

ESR > 40

CRP > 10

Blood cultures

Differential Diagnosis of the Painful TKA 

Surgical Diagnosis  

1.  Prosthetic loosening and failure 

2.  Infection 

3.  Patellofemoral tracking problems  

4.  Instability 

5.  Recurrent intra-articular soft-tissue impingement / Component overhang  

Nonsurgical Diagnoses  

1.  Referred pain - Hip / Back  

Epidemiology

Most common tumour of hand

F > M

2nd - 4th decade

Aetiology 

Unknown 

Trauma

Mucoid degeneration of collagen tissue

Synovial herniation

Location

Aetiology

Intrinsic

Infection

Loosening

Thigh pain in uncemented

- micro motion at distal end of stem

- modulus mismatch

Stress fracture / insufficiency fracture

- pubic rami, sacral

Intra-operative fracture

Prosthesis failure

Subtle instability

Extrinsic

Definition

Cystic structure lined by a mature capsule of dense fibrous tissue

- contains thick viscous fluid with a high mucopolysaccharide content

- fluid is a myxoid degeneration of synovial fluid

Epidemiology

Most common in young females

- peak age 15-30

- F:M = 3:1

Most common tumour in hand (2/3)

Aetiology

Unclear

AKA

Simple Bone Cyst

Definition

A simple bone cyst is a solitary cavity containing clear fluid

- originating in the metaphysis of growing children

- adjacent to the metaphyseal aspect of the growth plate.

Aetiology

Unknown pathological origin

Definition

Joint inflammation secondary pyogenic organism

Epidemiology

All age groups

Usually children

- 50% < age 3

M= F

Any joint

- Infants = Hip

- Children = Knee

- Adults = Large Joints

IVDU - SCJ & SIJ

Pathogenesis

Two Routes