RECURRENT DISLOCATIONS OF PATELLA

Dislocation of Patella
Dislocation of Patella is relatively rare event. This usually occurs in adolescent girls. There are predisposing factors like genu valgum and lateral mal tracking. The injury can occur in sports. External rotary force on flexed knee is the mechanism.
Patient presents with flexed knee, laterally displaced patella and prominent medial femoral condyle. Closed reduction is usually successful,
Immobilization is given with splint in full extension.
Open reduction is occasionally required. Indications being osteochondral fracture, loose body and joint incongruity.


Recurrent Dislocation of patella
Recurrent dislocation is common in adolescent girls. It is characterized by repeated incidents of complete lateral displacement of patella and frequent subluxations. Initial attack may be due to trauma causing an valgus strain on extended knee. Spontaneous reduction does occur. However the dislocation recurs due to predisposing factors.
Over a period patient suffers from anterior knee pain more on climbing or descending and feeling of give away.
Signs:
Tenderness over medial border of patella.
Lateral position of patella.
Tight or tethered lateral structures
Fairbanks apprehension test:
With knee held relaxed at twenty degrees of flexion. Patella is manually glided laterally. Patient complains of resistance and anxiety. This makes test positive.
Patellar glide test: A tight lateral ratinaculum will limit medial glide of patella. Usually, there is lateral hyper mobility.
Patellar tilt test: Tight lateral structures resists lateral tilting of patella.
Patellar mal tracking: Patellar movements are tested with knee flexion. Patella moves more laterally than superiorly.

Investigation
Radiograph of knee shows patella alta.
Blumensaat’s line : A radiograph is done with knee in 30 degree of flexion. A line drawn from intercondylar notch should touch lower end of patella. In patella alta, the line does not touch.
Insall and salvati index: The index is ratio of length of patella to patellar tendon . normally it is 0.8 to 1.0.
CT scan, MRI can be used to know dynamic mal tracking at different angles of flexion.

Management:
Conservative management if often used as initial method. Analgesics are prescribed for pain relief. Splinting is done after traumatic episode to allow soft tissue healing. Vastus medialis strengthening exercises are given to prevent lateral migration of patella.
Surgical method is used for active young athlete. There are various surgical procedures. They basically aim at releasing tight lateral structures and augmentation of medial structures. The end result is reposition of patella.