The patella articulates with the femur and especially with the femoral groove. It is an articular surface in which the patella slides as the knee flexes and extends. Sometimes the patella may be partially or completely dislocated after injury.
When the patella is dislocated it causes pain and inability to flex or extend the knee. Even in cases where it is automatically reconstituted – without orthopedic intervention – further treatment is needed.
ETIOLOGY
There are several ways in which the patella can be dislocated. Sometimes it takes minimal force to be dislocated, because of the structure of the child’s knee.
- Hypoplasia of the femoral condyles leading to an abnormal and “shallow” groove, a pathological condition that predisposes to instability or dislocation of the patella.
- The joints of some children are looser than normal, leading to a loose knee joint, which is prone to patellar dislocations. It is observed more often in girls during adolescence and often affects both knees.
- Children suffering from cerebral palsy or Down syndrome have more easily dislocated patellae, mainly due to generalized muscle weakness and imbalance.
- Very rarely, some children develop a congenital instability of the patella, leading to painless dislocations from a very young age.
In healthy children with normal knees, patellar dislocation is often the result of a direct hit or fall to the ground during sporting activities. However, the patella can be dislocated without immediate injury, e.g. as after a steep turn.
SYMPTOMS
Symptoms of the patient after patellar dislocation
Some of the most common symptoms are:
- Pain
- Feeling of instability of the patella. The patient feels that the patella slips out of place
- A rattling sound
- Edema
- Visible deformity of the joint – change in the image of the knee
CLINICAL EXAMINATION
Patellar dislocation is treated in the emergency room of the hospital because immediate intervention is required. Most of the times, however, it has automatically returned into place before a visit to the Orthopedist.
During the examination the physician asks for a detailed description of the injury mechanism and the child’s symptoms. He then examines the range of motion and sensitivity of the knee with respect to the patient’s pain.
IMAGING EXAMINATIONS
Radiographs: They allow for detailed images of the knee bones. Special shots (tangent plane) describe the relationship of the patella to the femoral groove.
Magnetic Resonance Imaging: They describe in detail soft tissues, such as ligaments. This is not a “first-choice” examination since it is not necessary for the diagnosis of the dislocation. However, it is required to exclude other concomitant lesions, such as free bodies from the articular cartilage of the patella within the joint.
TREATMENT
IMMEDIATE TREATMENT
In the event of a knee injury, the young patient should be treated in the emergency department. Before any treatment, the orthopedist prescribes analgesic drugs and then gently reduces the patellar dislocation.
NON-SURGICAL TREATMENT
IMMOBILIZATION: The doctor applies a splint for 3 to 4 weeks which stabilizes the knee until the pain subsides.
DISCHARGE CARE: Charging the affected leg can cause pain and slow down the recovery process. This is why it is sometimes recommended to use crutches.
PHYSIOTHERAPY: After the immobilization period, the Orthopedist recommends physiotherapy to help the child regain strength and range of motion. Special exercises help to strengthen the muscles of the thigh. The patient’s compliance with the physiotherapy program is important for the return to sports activities, which is achieved in 3 to 6 weeks.
The patellar dislocation causes injury to the ligaments that hold it in place and thus the joint becomes increasingly unstable after repeated injuries. As a result, the patella is dislocated by injuries of less and less force. Recurrences are more common in children with anatomical abnormalities of the knee joint. Continuous knee training, such as cycling, can strengthen the quadriceps and prevent patellar dislocations.
SURGICAL TREATMENT
If the child’s knee is severely unstable at the knee joint, despite conservative treatment, then surgical repair is recommended and the type of surgery will depend on the causes that led to the instability.
Surgical recovery includes reconstruction of the ligaments that hold the patella in place. This operation is often performed arthroscopically using a small camera and special surgical tools inserted into the joint through small incisions.
Recurrent patellar dislocations due to anatomical variations and abnormalities may require more complex surgeries.