Patellar Fracture mechanism
- direct blow to the patella: fall, MVC (dashboard)
* indirect trauma by sudden flexion of knee against contracted quadriceps
Patellar Fracture clinical features
- marked tenderness
- inability to extend knee or straight leg raise
- proximal displacement of patella
- patellar deformity
- ± effusion/hemarthrosis
Patellar Fracture investigations
• X-rays: AP, lateral, skyline
do not confuse with bipartite patella: congenitally unfused ossification centres with smooth margins on X-ray at superolateral corner
Patellar Fracture treatment
• non-operative
■ indication: non-displaced (step-off <2-3 mm and fracture gap <1-4 mm)
◆ straight leg immobilization 1-4 wk with hinged knee brace, weight bearing as tolerated
◆ progress in flexion after 2-3 wk
◆ physiotherapy: quadriceps strengthening when pain has subsided
• operative
■ indication displaced (>2 mm), comminuted, disrupted extensor mechanism
■ ORIF, if comminuted may require partial/complete patellectomy
• goal: restore extensor mechanism with maximal articular congruency
Complications of patellar fracture
- Symptomatic wiring
- Loss of reduction
- Osteonecrosis (proximal fragment)
- Hardware failure
- Knee stiffness
- Nonunion
- Infection
Types of patellar fractures
undisplaced
vertical
lower/upper pole
comminuted displaced
transverse
osteochondral
Patellar dislocation mechanism
- usually a non-contact twisting injury
- lateral displacement of patella after contraction of quadriceps at the start of knee flexion in an almost straight knee joint
- direct blow, e.g. knee/helmet to knee collision
Patellar dislocation risk factors
- young, female
- obesity
- high-riding patella (patella alta)
- genu valgus
- Q-angle (quadriceps angle) ≥20°
- shallow intercondylar groove
- weak vastus medialis
- tight lateral retinaculum
- ligamentous laxity (Ehlers-Danlos)
Patellar dislocation clinical features
- knee catches or gives way with walking
- severe pain, tenderness anteromedially from rupture of capsule
- weak knee extension or inability to extend leg unless patella reduced
• positive patellar apprehension test
■ passive lateral translation results in guarding and patient apprehension
- often recurrent, self-reducing
- concomitant MCL injury
- increased Q-angle
- J-sign
What is the Q angle
The angle between a vertical line through the patella and tibial tuberosity and a line from the ASIS to the middle patella; the larger the angle, the greater the amount of lateral force on the knee (normal <20°)
Patellar dislocation treatment
• non-operative first
■ NSAIDs, activity modification, and physical therapy
■ short-term immobilization for comfort, then 6 wk controlled motion
■ progressive weight bearing and isometric quadriceps strengthening
• operative
■ indication: if recurrent or if loose bodies present
■ surgical tightening of medial capsule and release of lateral retinaculum, possible tibial tuberosity transfer, or proximal tibial osteotomy
Patellofemoral syndrome (Chrondromalacia Patellae) description
syndrome of anterior knee pain associated with idiopathic articular changes of patella
Patellofemoral syndrome (Chrondromalacia Patellae) risk factors
- malalignment causing patellar maltracking (Q angle ≥20°, genu valgus)
- post-trauma
- deformity of patella or femoral groove
- recurrent patellar dislocation, ligamentous laxity
- excessive knee strain (athletes)
Patellofemoral syndrome (Chrondromalacia Patellae) mechanism
- softening, erosion, and fragmentation of articular cartilage, predominantly medial aspect of patella
- commonly seen in active young females
Patellofemoral syndrome (Chrondromalacia Patellae) clinical features
• deep, aching anterior knee pain
■ exacerbated by prolonged sitting (theatre sign), strenuous athletic activities, stair climbing, squatting, or kneeling
- insidious onset and vague in nature
- sensation of instability, pseudolocking
- pain with extension against resistance through terminal 30-40°
- pain with compression of patella with knee ROM or resisted knee extension
- swelling rare, minimal if present
- palpable crepitus
Pain with firm compression of patella into medial femoral groove is pathognomonic of patellofemoral syndrome
Patellofemoral syndrome (Chrondromalacia Patellae) investigations
- X-ray: AP, lateral, skyline – may find chondrosis, lateral patellar tilt, patella alta/baja, or shallow sulcus
- CT-scan
- MRI – best to assess articular cartilage
Patellofemoral syndrome (Chrondromalacia Patellae) treatment
Treatment
• non-operative
■ continue non-impact activities; rest and rehabilitation
■ NSAIDs
■ physiotherapy: vastus medialis and core strengthening
• operative ■ indication: failed non-operative treatment ■ tibial tubercle elevation ■ arthroscopic shaving/debridement ■ lateral release of retinaculum
