Usually occurs in patients over 60
- due to decreased vascularity & collagen weakness
Younger patient on steroids / growth hormone
Occasionally occurs in young athlete with excessive contracture
Often preceded by quadriceps tendinosis
Direct blow
- most common
Indirect
- forced knee flexion with foot fixed / maximally contracted quadriceps
1. Vertical
2. Transverse
1. Loosening
2. Infection
3. Instability
4. Periprosthetic fracture
5-15% of posterior dislocations
Posterior hip dislocation
Type I - head fracture below fovea
Undisplaced
- non operative
Displaced
- excise fragment if small
- ORIF fragment if large (can contribute to instability)
Rheumatoid arthritis
Combined ankle and subtalar joint osteoarthritis
Calcification
- central pattern
- often increased opacity compared with bone
Ossification
- peripheral pattern
- similar density to bone
Pathological bone formation in soft tissues
In elbow
- 3% of trauma
- 89% if head injury + trauma
Completely different
1. Myosisitis Ossificans Circumscripta
- post traumatic
- more common
- recognised as a consequence of neurological injury
Multi-ligament knee injury (MLKI)
- 2 or more ligaments disrupted
Knee dislocation
- ACL + PCL + one of collaterals
High energy (MVA)
Low energy (sport)
- low energy has 5% arterial injury
Pigmented Villo-Nodular Synovitis
- benign inflammatory process that arises in synovial tissues
- contains significant amounts of hemosiderin
Age: 20 - 50
Sex: M > F
A. Diffuse
- throughout joint synovium
- more difficult to treat / excise fully
Chondroid Metaplasia of synovium affecting large joints
Nodules of hyaline cartilage
- formed in the subsynovial layer of joint capsules
Rare lesion
Most common in 20's and 30's
Sex: M > F (2:1)
Monoarticular