Patellar dislocation are a violation of the relationship between the inner surface of the patella and the anterior surface of the tibia. Dislocation can be lateral, vertical or torsion. Regardless of the type of dislocation, the injury is accompanied by a pronounced pain syndrome, soreness and inability to move in the knee joint, palpation-determined displacement of the patella. The support on the leg is sometimes partially preserved. The diagnosis is made based on the results of the examination and radiography data. The treatment consists in setting the patella and fixing it with a plaster cast. In some cases, the operation is shown.
S83.0 Patellar dislocations
Patellar dislocation account for 0.4-0.7% of the total number of dislocations. The patella is a small rounded flat bone located on the anterior surface of the knee joint. The tendons of all four heads of the quadriceps femoris are attached to the patella from above. Tendon fibers cover the patella from all sides and form their own patellar ligament in the area of its lower pole. The patella is located in a small depression, held in place by the tendons of the quadriceps muscle and supporting ligaments (external and internal). The condyles of the femur play a certain role in limiting the mobility of the patella.
As a rule, the cause of dislocation of the patella is a direct injury (a fall on the knee joint, a side impact in the patellar region), combined with a contraction of the quadriceps muscle. Lateral dislocation of the patella usually occurs when the lower leg is bent. When bending in the knee joint, lateral dislocation is practically impossible, since the knee pad is tightly pressed against the intercondylar surface of the femur. In rare cases, with a bent lower leg, vertical dislocation of the patella is possible.
The probability of dislocation of the patella increases with a shallow patellar cavity, a poorly developed external condyle of the thigh, a violation of the relationship between the axis of the quadriceps muscle and its own patellar ligaments. Usually, until the moment of injury, these anatomical features do not manifest themselves in any way and remain unnoticed.
In traumatology and orthopedics, acquired (traumatic) and congenital dislocations of the patella are distinguished. Depending on the prescription of the injury, acute and long-standing dislocation of the patella is distinguished. If the dislocation occurs repeatedly, they talk about the usual dislocation. According to the direction of displacement, there are:
- lateral dislocations of the patella (external and internal);
- torsion (rotational) dislocations, in which the patella rotates around its vertical axis;
- vertical dislocations, in which the patella turns around its horizontal axis and wedges into the articular gap between the tibia and femur.
Most often there is an external, less often an internal dislocation of the patella. Torsion and vertical dislocations of the patella are extremely rare.
Patellar dislocations symptoms
Acute traumatic dislocation is accompanied by sharp pain. The knee joint is slightly bent, enlarged in volume, expanded in the transverse direction (with lateral dislocations). Active movements are impossible, passive ones are painful and sharply limited. The direction and degree of displacement of the patella is determined by palpation. With a complete dislocation, the patella is located outward from the lateral condyle of the thigh, with an incomplete one, it is located above the lateral condyle.
Sometimes a traumatic dislocation of the patella is corrected independently. Patients in such cases note an episode of sharp pain in the leg, which was accompanied by a feeling of buckling and displacement in the knee. After a self-corrected dislocation of the patella, there is a slight or moderate swelling in the knee joint area. Possible hemarthrosis (accumulation of blood in the knee joint).
The diagnosis of patellar dislocation is made by an orthopedic traumatologist based on a characteristic anamnesis, clinical picture and radiography data. The most informative are comparative radiographs of both patellae, carried out with the tangent direction of the X-rays from the front and from top to bottom or from bottom to top.
The basis for diagnosing a habitual dislocation is repeated dislocations of the patella that occur without a pronounced traumatic effect. Habitual and long-standing dislocations of the patella may be an indication for an knee MRI. When deciding on the feasibility of surgery, diagnostic knee arthroscopy is performed.
Patellar dislocations treatment
Acute dislocation is usually treated conservatively. Dislocation is corrected under local anesthesia. The limb is bent at the hip joint (to loosen the tension of the tendons of the quadriceps muscle) and unbent at the knee joint. Then gently shift the patella until the dislocation is eliminated and a plaster cast is applied.
After the reduction, a control radiograph is necessarily prescribed to confirm the reduction of dislocation and to identify bone-cartilaginous bodies that sometimes form during injury. With acute dislocation of the patella, immobilization is indicated for a period of 4-6 weeks. Massage and physiotherapy are carried out under the supervision of a physiotherapist, without removing the splint. The full load on the leg is allowed a month after the injury.
Surgical treatment of acute patellar dislocation is carried out when bone-cartilaginous bodies are detected and there is a high probability of repeated dislocations due to changes in the knee joint. Long-standing and habitual dislocations of the patella are an indication for surgical treatment. After the operation, immobilization is indicated for a period of 4-6 weeks. The full range of movements in the knee joint is allowed after 8-10 weeks.