▎ WuXi AppTec content team editor
In life, many people may have had the experience of suddenly "soft" their knees when walking, what is the reason?
In fact, this is a manifestation of knee instability, there are many reasons, such as ligament damage, quadriceps muscle weakness and so on.
One of the most common problems is related to the "round bone" that protrudes from our knees – the patella (kneecap).
What is a patellar dislocation?
Normally, the patellofemoral joint consists of the patella and the femur (thigh bone).
The patella is located in a femoral sled (that is, a groove, or groove, track) above the femur, and the complex network of ligaments, tendons, and other soft tissues around it is "tied" together.
Image credit: References[1], translated by WuXi AppTec's content team
It can stand still, or it can move smoothly in small areas on this track, like a tram.
It is closely connected to the quadriceps muscle on the front of the thigh, helping to transmit the strength and stability of the quadriceps muscle when the knee is extended and bent.
But sometimes, the patella will deviate from its normal orbit, causing the patella-femoral joint to be unstable, and it will feel like the knee suddenly "softens":
Patella subluxation: The patella partially slides out, but does not slide completely out of orbit. This partial dislocation can cause pain, swelling, bursting, or stiffness in the knee joint.
Patellar dislocation: This is a traumatic injury due to high impact, with damage to soft tissues present. It is equivalent to the patella being completely "derailed" and then forcibly returned to its original position. During the process, because the patella tends to dislocate outward, the medial ligament located on its medial side of the patellofe is torn or stretched.
What are the symptoms of patellar subluxation or dislocation?
The first time a patellar dislocation occurs, it often occurs during exercise, when they feel a sudden weakness in the knee and then fall.
(Note: This process is similar to a tear in the anterior cruciate ligament, which is more common than patellar dislocation, so it needs to be investigated first to avoid misdiagnosis.) In rare cases, patients who have torn anterior cruciate ligament are accompanied by patellar dislocation. ）
At this time, the knee will appear obviously swollen and painful, and some people will not dare to straighten their knees or bend, and they will not be able to stand up and walk.
Image credit: 123RF
When you go to the hospital for examination, you will have a positive response to the "patella extrapolation fear test" (in this test, the orthopedic surgeon will gently push the patient's patella outward while the knee is flexed 20 degrees, trying to mimic the dislocation process). If the patient develops anxiety reactions, pain, or fear, it suggests a dislocation of the patella).
But there are also many people who have their knees straightened, and they will automatically reset, and they will hear a "click".
What are the causes of patella dislocation?
1. Acute patellar dislocation caused by external forces
For example, when we are moving quickly in a semi-squat, making sharp turns (especially football, basketball and other sports), if the side of the knee is hit, or suddenly falls during exercise, the knee lands, which may cause acute patellar dislocation, which is often the case of young people.
2. There is a problem with the knee joint itself
For example, femoral sledgepod dysplasia (such as "track" is too shallow, easy to "derail"), medial femur muscle hypoplasia, high patella; natural relaxation of ligament joints (more common in young women).
In addition, some patients may also have femur and tibia deformities, such as knee valgus and femur tilt (calf rotation), which can put too much pressure on the medial patellofemoral ligament.
This is a complex patellomoral joint instability, prone to recurrent seizures, often requiring cross-disciplinary collaborative treatment.
These deformities may not be seen on routine X-rays or magnetic resonance imaging (MRI) and generally require a special CT scan.
If these deformities are not corrected, even with patellofemoral surgery, the results may not be too good and may lead to ligament reconstruction failure and further dislocation.
How is patellar dislocation treated?
The first dislocation is generally treated conservatively, including splint brace fixation, discharge of swelling fluid, taking painkillers, physical therapy, etc.
Because in most cases, the patella is easier to reset, and the torn ligament heals on its own. Among them, physical therapy often needs to be continued for 2 to 3 months.
However, some people may also have bone or cartilage fractures, or recurrent dislocations, bone deformities, etc., which requires doctor evaluation and consideration of surgical treatment. The postoperative recovery time is about 6 to 9 months, and it is also necessary to cooperate with physical therapy.
Avoid patellar dislocation, what should you pay attention to in life?
1. For the general population
Be sure to warm up before exercising, pay attention to protecting your knees, especially sports that require rapid running and jumping, do not be too intense, and wear knee pads if necessary;
Usually, you can do some actions to strengthen the strength of the muscles around the knee joint, such as half-squatting against the wall;
If possible, try to choose swimming, flat bikes, scooters and other sports that have little knee damage, especially obese people, and reduce weight through these exercises to reduce the pressure on the knee joint.
2. For people who have experienced patellar dislocation
It is best to strengthen the exercise of quadriceps under the guidance of a rehabilitation therapist;
Long-term practice of gentle stretching exercises such as yoga or tai chi to maintain the flexibility of joints and muscles;
When squatting on the toilet, slow down, do not buckle your knees;
Avoid sports that fall to the ground in a knee-rolled-out position (such as vaulting horses) and sports that require calf rotation (such as when playing golf and turning around);
Patellar dislocation in the elderly can easily lead to falls, go out with crutches, choose good support, non-slip shoes.
Image credit: 123RF
Resources
[1] Crossley, K. M.,Callaghan, M. J., & van Linschoten, R. (2016). Patellofemoral pain. Britishjournal of sports medicine, 50(4), 247-250.
[2] PatellofemoralInstability. Retrieved Apr 12 from https://www.hss.edu/conditions_patellofemoral-kneecap-instability.asp
[3] ComplexPatellofemoral Instability: A Collaborative Approach. Retrieved Apr 12 from https://www.hss.edu/conditions_complex-patellofemoral-instability-collaborative-approach.asp
[4] Walking knee joint is always soft, easy to fall, beware of patellar dislocation- Peking University Third Hospital. Retrieved Apr 12 from https://mp.weixin.qq.com/s/dyJWWXRTGJA0atGldi4UjQ
[5] Don't IgnoreBuckling Knees. Retrieved Apr 12 from https://www.healthcentral.com/article/dont-ignore-buckling-knees
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