Acute patellar dislocation

　　First, etiology

　　Primarily due to direct violence, occasionally due to indirect violence.

　　Second, pathogenesis

　　1. Action of violence:Or the presence of structural abnormalities can lead to traumatic patellar dislocation. However, it should be noted that the magnitude of violence can vary greatly, and most cases have potential abnormalities in skeletal, fascial, or muscular structures, such as a flat patellar tubercle of the femur. Excessive external rotation of the tibia, fibrous bands pulling on the lateral side of the patella, absence or weakness of the patellar insertion fascia of the medial quadriceps muscle, and increased Q-angle. Poor strength of the quadriceps muscle, multiple joint laxity, and other conditions.

　　2. Mainly due to trauma:Direct violence is characterized by blows to the anterior, medial, or lateral sides of the patella; occasionally, indirect violence, such as the strong contraction of the quadriceps muscle, can cause the patella to dislocate outward. Rupture of the quadriceps tendon and tear of the distal patellar retinaculum can lead to the patella dislocating downward. Those caused by direct violence often have associated fractures in other parts, such as fractures of the femur and tibia, and hemarthrosis within the joint cavity.

　　3. Traumatic patellar dislocation:The direction depends on the direction of the direct force and the flexion and extension state of the knee joint. Generally, it is divided into six types: lateral, medial, superior, inferior, intra-articular, and intercondylar dislocation. If the force comes from the medial or anteromedial side, it leads to lateral dislocation of the patella, which is most common in clinical practice. If the force comes from the lateral side, it causes the patella to dislocate medially, which is rare in clinical practice. Rupture of the quadriceps tendon and the distal part of the quadriceps tendon can cause the patella to dislocate medially and inferiorly, while patellar tendon rupture can lead to superior dislocation of the patella. When direct force causes patellar dislocation and the dislocated patella rotates during the flexion and extension of the knee joint, it can cause intra-articular patellar dislocation and intercondylar dislocation of the femur, which is extremely rare in clinical practice.

　　1. Recurrent patellar dislocation:When the knee joint is flexed and extended, the patella moves up and down in the groove of the distal end of the femur. Due to the anatomical structure of the patella, the action of the quadriceps muscle and the joint capsule, it maintains stability during movement. The central part of the patella joint surface is a longitudinal ridge-like convexity, which matches the corresponding joint surface of the distal end of the femur to prevent the patella from sliding laterally. The contraction of the quadriceps muscle is mainly due to the traction of the quadriceps muscle, preventing the patella from dislocating outward. The tension of the joint capsule during muscle contraction also plays a stabilizing role in the patella, but due to trauma and pathogenic factors of the knee joint, whether congenital or acquired, recurrent patellar dislocation can occur.

　　2. Osteoarthritis:Due to aging or other reasons such as trauma, congenital abnormalities of the joint, joint deformities, etc., non-inflammatory degenerative changes of articular cartilage and osteophyte formation at the joint margin can occur, which can cause symptoms such as joint pain, limited movement, and joint deformities in clinical practice.

　　1. Local knee joint:Patients with acute patellar dislocation presenting with symptoms may only show local ecchymosis and tenderness due to the fact that most have returned to their original position.

　　2. Abnormal appearance:A few patients may have knee joint elastic flexion deformity, a feeling of emptiness in front of the patella, and can feel the dislocated patella on the lateral side of the knee joint.

　　For dislocations caused by congenital causes, there are no effective preventive measures for this disease, so the prevention of this disease is mainly aimed at traumatic etiology-induced acute dislocation. Avoiding trauma is the key to the prevention and treatment of the disease. In addition, attention should be paid to both effectively correcting the dislocation and maintaining the normal patellofemoral joint structure during correction, keeping the patellofemoral joint alignment normal, avoiding postoperative knee pain and patellofemoral arthritis, and quickly restoring function.

　　In addition to relying on clinical manifestations, auxiliary examinations are also needed for diagnosis. The X-ray film of this disease can show the dislocated patella and varying degrees of swelling in the knee joint. This disease seriously affects the patient's daily life, so active prevention is necessary.

　　What kind of food is good for the body for acute patellar dislocation?

　　Nutrition should be enhanced, and more protein-rich foods such as fish, eggs, bean products, and appropriate calcium should be increased. Drink more water and eat more vegetables and fruits such as green vegetables, celery, and bananas.

　　2. What foods should be avoided for acute patellar dislocation?

　　Avoid spicy foods: such as chili, mustard, etc. Smoking and drinking should be戒除.

　　1. Non-surgical Management

　　Dislocation can often be reduced manually, and the patella dislocation can be reduced by pressing the lateral edge of the patella when the knee joint is in extension. Then, the thigh splint is fixed for 4 to 6 weeks. And X-ray films should be carefully examined to exclude the presence of osteochondral fragments remaining in the joint. Try to avoid recurrent patellar subluxation or complete dislocation in the future. However, it should be noted that conservative treatment methods often ignore the injury of the patellar medial support band and cannot correct developmental patellar malposition or patellofemoral alignment.

　　2. Surgical Management

　　When there are osteochondral fragments in the knee joint, surgical resection or repair should be performed, and the torn soft tissues on the medial side of the knee, including the medial expansion of the quadriceps femoris, should also be repaired during the operation. If necessary, lateral support band relaxation and medial support band tightening can be performed to reduce the tensile force on the patella outward. If the patellar dislocation cannot be reduced manually, surgical incision reduction should also be performed, and the torn soft tissues should be repaired at the same time. For recurrent patellar dislocation after trauma, only surgery can be effective. Through lateral relaxation, medial tightening, and patellar repositioning surgery to correct the patellofemoral joint relationship. The indications for surgery for patellar instability include:

　　1. Acute dislocation with medial support band rupture or osteochondral fracture of the femur or patella.

　　2. Recurrent dislocation or subluxation or associated joint injury, including meniscus injury and osteochondral fracture.

　　3. Surgical Methods:

　　If the bony structure of the patient's knee joint and the development of the Q-angle are normal, ideal results can be achieved through simple medial repair or tightening, plus lateral support band incision and relaxation. For cases with congenital Q-angle abnormalities and other conditions, the treatment should be according to recurrent patellar dislocation to avoid recurrent patellar dislocation after surgery.