Educational video describing conditions and treatment of patellar dislocation.
The patella is a protective bone located in front of the knee joint. The patella is attached to the quadriceps muscle through the quadriceps tendon. The patella facilitates the function of the quadriceps to straighten the knee. The patella lies within the patellofemoral groove. This groove allows the patella to slide vertically with normal movement of the knee joint.
Dislocation of the patella occurs from the patella sliding laterally out of its position on the knee. It may occur from a blow to the knee, acute trauma or severe twisting of the knee.
In majority of the cases dislocation is associated with pain, swelling and a lump on the lateral side or outer side of the knee.
The patella will usually relocate by itself back into the normal position in the groove as the patient straightens the knee.
Sunrise view demonstrates lateral dislocation of the patella. X-rays should be carefully evaluated for the presences of osteochondral fragments displaced within the knee joint.
Mechanism of patellar dislocation:
•Medial patellofemoral ligament failure.
•Lateral dislocation of the patella may also cause direct impaction injury to both the medial patella and lateral femoral condyle.
Causes of patellar dislocation
•Weak VMO muscle (vastus medialis oblique).
•Large Q angle ( normal male 14- female 17)
•Excessive foot pronation
•Patella alta
•Genu valgum (knock knee)
Treatment
•First episode is treated nonoperatively unless there is a loose fragment inside the joint which should be removed surgically
•Use knee immobilizer or a brace for 2-3 weeks to allow medial structures and ligament to heal.
•Quadriceps strengthening exercises.
Complications
•50% of the patients treated conservatively will have recurring episodes of instability and some patients will require surgery.
•Common complication of patellar dislocation is chondromalacia.