Why does the patella pop out?
Normally, the patella slides along the groove at the end of the femur, like a train on tracks. It is held in place by the shape of this groove, the tension of the medial retinaculum ligament from the inside and the traction of the inner part of the quadriceps muscle. If the groove is flat, the patella is too high, the tibia is turned outward, or the legs have a valgus shape, the balance is disturbed and the cup tends to move outward. A sharp turn is enough for her to jump off. The first time a dislocation occurs, the medial ligament is torn, and without repairing it or strengthening the muscles, the risk of recurrence remains high, especially in adolescents.
- Flat or underdeveloped femoral groove
- High position of the patella
- Valgus deformity of the legs and outward rotation of the tibia
- Weakness of the inner head of the quadriceps muscle
- Joint hypermobility and connective tissue weakness
- Rupture of the medial retinaculum ligament during the first dislocation
Symptoms
At the moment of dislocation, there is a sharp pain and a feeling that the knee has twisted or something has shifted to the side. The leg may give way and the person falls. If the cup remains displaced, the knee appears deformed and is fixed in a bent position. Often the patella snaps back into place on its own when you try to straighten the leg, and all that remains is pain and rapidly growing swelling. Blood in a joint indicates a ligament tear or cartilage damage. After reduction, fear, uncertainty and pain remain along the inner edge of the cup.
- Sensation of cup displacement and wobbly leg
- Sharp pain in the knee
- Knee deformity with persistent dislocation
- Rapid joint swelling
- Pain along the inner edge of the patella
- Feeling unsure when turning and squatting
Diagnostics
After reduction, an X-ray of the knee is required, including axial alignment of the patella: it shows the shape of the groove and the position of the cup. The main study is MRI: it reveals a rupture of the medial retinaculum ligament, areas of bone swelling in characteristic places after dislocation and, most importantly, avulsion of an osteochondral fragment that can become a loose body in the joint. CT is used for accurate measurements when planning surgery in patients with repeated dislocations. During the examination, the axis of the legs, the flexibility of the joints and the strength of the thigh muscles are assessed.
- X-ray of the knee with axial positioning of the patella
- MRI of the knee joint as the main method
- CT for measurements when planning surgery
- Ultrasound to evaluate effusion and ligaments
- Assessment of leg axis and joint hypermobility
- Test for patellar displacement during examination
Treatment of the first dislocation
If the cup does not straighten itself, the doctor returns it to its place, carefully straightening the leg. The knee is then immobilized with a brace for several weeks, allowing walking with support. If the joint is tense, a puncture is performed. As soon as the pain subsides, physical therapy begins: focusing on the inner quadriceps, gluteal muscles, and controlling the position of the knee when squatting. Surgery is usually not required for the first dislocation, but it is necessary if a torn osteochondral fragment is found in the joint - it is fixed or removed arthroscopically.
- Reduction of the patella by a doctor
- Orthosis for 3–6 weeks with walking allowed
- Joint puncture for tense hemarthrosis
- Strengthening the quadriceps and gluteal muscles
- Arthroscopy for avulsion of an osteochondral fragment
- Gradual return to sports
Repeated dislocations and prevention
If dislocations recur, conservative treatment is usually not enough, because the cause lies in the structure of the joint. In such cases, plastic surgery of the medial femoral-patellar ligament is performed using one’s own tendon, and in case of pronounced deviations, it is supplemented by moving the tibial tuberosity or correcting the shape of the groove. The choice of surgery depends on the results of CT and MRI measurements. Regardless of tactics, long-term work on the strength of the hip and pelvic muscles, landing control and movement technique is required - without it, the risk of repetition remains.
- Plastic surgery of the medial femoral-patellar ligament
- Relocation of the tibial tuberosity according to indications
- Correction of the shape of the groove in cases of severe dysplasia
- Long-term program to strengthen the hip and pelvic muscles
- Landing and turning technique training
- Orthosis or taping when returning to sports