patella

Mechanism

1. Direct lateral blow to patella

- usually with knee partly flexed and quadriceps relaxed

2.  Indirect low energy injury

Definition

Repeated dislocation of patella with minimal trauma

- 15-20% of paediatric acute patella dislocations

- more common girls 

- often bilateral

Dislocation occurs unexpectedly when quadriceps contracted with knee in flexion 

Direction

Mechanism

Direct blow

- most common

Indirect

- forced knee flexion with foot fixed / maximally contracted quadriceps

Types

1.  Vertical

2.  Transverse

Region specific approaches

Theory

- want to traverse one muscle / one compartment

- keep away from NV bundle

- as a rule perform open biopsy through compartment the tumour is in

- this is the compartment that will require surgical removal in wide excision

- direct approach without going through muscle if possible i.e. tibia, distal ulna

Lower Limb

Thigh

Ossification

Patella may develop from one or multiple ossification centres at 3 years

Failure of centres to fuse may produce bipartite or tripartite patella

- usually bilateral and painless

Classically superolateral

Classification Saupe

I   Inferior Pole 5%

II  Lateral 20%

Epidemiology

Active pre teen boy

- activity related pain

- common in high jumpers

Diagnosis

Fragmentation / calcification of inferior pole

- repetitive traction injury where PT inserts

- tender at this point

Stages 

I     Normal

II    Ca inferior pole irregularity

III   Coalesce Ca inferior pole

Definition

Patellar Tendinitis

Epidemiology

Most common in athletes

- especially if involved in running, jumping and kicking

- over use injury

Basketball players

Aetiology

Chronic overload v inferior patella impingement

Schmidt et al Am J Sports Med

- dynamic MRI in patients with jumper's knee v controls

- no evidence of impingemnt

Non-operative

Results

90% respond 

- very important

- 6 - 12 months minimum before offering surgery

Physiotherapy

1.  Stretches

- quads stretches

- ITB

- lateral retinaculum

AP / Long Leg Views

Quantify Valgus Malalignment

Lateral Xray

1.  Assess Patella Alta

30^o flexion

Epidemiology

Usually occurs in young people

- often previous history of tendonitis ± steroid injections

Location

Usually at level of inferior pole of patella

- less common at tibial tubercle

- mid-substance ruptures rare

Clinical

Severe pain

Palpable defect

Extensor deficit / unable to SLR

Xray

Patella alta / high riding patella