Definition
Softening and fibrillation of articular cartilage of patella
Problem
- softening and fibrillation often seen in asymptomatic population
- can have typical anterior knee pain without retro-patellar changes
Epidemiology
Female adolescent
- recent increase in activity
Query on continuum to OA
May be a separate pathology
Aetiology
Unknown / varied
Mechanical
Acute
- direct trauma
- PFJ dislocation
Chronic
- PFJ instability / chronic maltracking
- LPPS (lat patellar pressure syndrome)
- quadriceps imbalance
- VMO weakness
Biological
Idiopathically abnormal cartilage unable to tolerate load
- inflammatory arthritis
- recurrent haemarthrosis
- sepsis
Iatrogenic
- repeated intra-articular steroids
- prolonged immobilisation
Degenerative
- primary OA
Pathology
Basal degeneration of cartilage at deep level
- pain due to nerve endings in subchondral bone being stimulated by variations in pressure
Classification
Grade 1
- localised softening with no break in surface
Grade 2
- fibrillation or fissured
Grade 3
- fissuring to bone
- crab meat appearance
Grade 4
- bone exposed / full thickness chondral defect
Symptoms
Anterior Knee Pain
Non-specific
- dull aching discomfort anterior knee
- cinema sign / sitting flexed generates pain
- stairs
- catch & pseudo-locking
- swelling
Signs
PFJ crepitus
- seen in 60% asymptomatic teens
Exclude malalignment
Xray
Exclude malalignment
Management
Non-operative
NSAIDS
Quadriceps exercises
Activity modification
Cut out brace & taping
Injections
- cortisone - last 2 - 6 weeks
- Hyaluronic acid - last 3 - 6 months
Operative
Options
Patellar Shaving
Federico et al Am J Sports Med 1997
- arthroscopic shaving in 36 patients with grade 2 or worse
- no malalignment
- all had some improvement
- only 50% good or excellent result
Unlikely to be a good option
Full thickness localised chondral defect
Subchondral Drilling / Abrasion
MACI
Gobi et al Am J Sports Med 2009
- chondral lesions on patella and trochlea
- all had reasonable symptomatic results
- tended to decline over time in patella and with multiple lesion
Other
Lateral Release
Indications
- chronic maltracking
OE
- tight lateral retinaclum
MRI
- tilt / lateral subluxation
- full thickness chondral lesion lateral facet
Fulkerson's osteotomy
Anteromedialisation of the tibial tubersity
TKR / PFJ replacement