Injury Prevention: Patella Dislocation


Knee injuries of all severity are rather common in the sports industry. One that you don't hear quite as often is a patella (kneecap) dislocation. However, for those of us who are LA natives, the name Andrew Bynum may come to mind when you hear patella dislocation. In January of the 2008 season, Bynum suffered a dislocation that initially took him out for 8 weeks. Other surgeries of the knee ended up taking him out for the remainder of the season.

What exactly is a patella dislocation and how does it differ from a knee dislocation?

The anatomy of the patella

The largest joint of the human body is also one of the most easily injured structures of the body. What joint is that? The knee. The knee is made up of 4 different structures that can each be injured dependently or independently of one another including tendons, ligaments, bones, and cartilage.

In humans, the patella (kneecap) is the largest sesamoid bone within the body meaning the bone is embedded in a tendon - specifically the quadriceps tendon. Triangular in shape, the patella rests between the tibia (shin bone) and the femur (thigh) which has a groove specifically for the patella to slide as the knee bends.

When someone says they dislocated their patella, what does that mean?

Put into the simplest terms, when someone dislocates their patella it typically means that the patella is moved from its normal position (typically laterally). When someone only partially dislocates their patella, it is referred to as a subluxation. In a subluxation, the kneecap typically returns to it's normal position by itself.

Further, a patellar dislocation most commonly occurs in females. Consider the anatomical structure of a male vs. a female, specifically the hips/pelvis. In females, the angle from the hip to the middle of the knee, also known as the Q angle, is greater than in males. The greater angle results in more stress laterally on the knees which can lead to a lateral sublaxation of the kneecap.

What's the difference between a knee dislocation and a patella dislocation?

When someone suffers a total knee dislocation, it is typically much more severe than a patella dislocation. A total knee dislocation means that the tibia and femur no longer touch resulting in a more extreme deformity than with a patella dislocation. In a total knee dislocation, it is not uncommon for surrounding structures such as tendons or ligaments to also suffer damage.

What causes a patella dislocation?

There are a number of different reasons a patella dislocation may occur.

1) Anatomical structure

There are a few different anatomical reasons why the patella may dislocate. As described above, a female with a wider hips may experience a patella dislocation without any major event. Also, if the groove that houses the patella is either shallow, misshapen, or not in the correct position, the kneecap may be more apt to slipping out of place.

2) Twisting of the knee

Similar to a meniscus tear, the patella may dislocate when the foot is planted and the knee twists. This is common in many sports including dance.

3) Direct trauma to the knee

When the knee joint collides with another object, the force to the front of the knee may force the kneecap to dislocate.

4) Weak or imbalance of the leg muscles

If the leg muscles cannot help support the knee and the kneecap, the chance of the patella dislocating increase. For example, if the quadricep is tight but the inner thigh is weak, the excess pull from the quadricep could cause your knee to dislocate.

What are the symptoms of a patella dislocation?

Symptoms of a patella dislocation may include:

  • Incorrect positioning/sliding of the kneecap

  • Stiffness

  • Swelling

  • Knee buckling

  • Unstable or inability to put weight on the leg

  • Cracking or popping sounds within the knee

  • Tenderness

  • The kneecap is easily moved (hypermobile)

  • Unable to to bend or straighten your knee

  • Catching when bending or straightening the knee

How can you prevent a patella dislocation?

If you've ever dislocated your patella (kneecap), you've probably been told that since it's happened once, it will most likely happen again. Frustrating? Yes! But, there are things you can be doing to avoid it from happening again.

1) Strengthen the leg muscles EVENLY

When you keep the muscles of the leg strong, they act as support for all of the other components of the leg. A crucial part of strengthening the muscles though is strengthening them evenly. They say you should "never skip leg day," but what they should really be saying is "never skip a muscle group of leg day."

For example: if you were to strengthen all of the muscles of the leg except the inner thigh, you may experience some "pulling" to the exterior of your leg which may result in higher frequency and likelihood of a patella dislocation.

2) Practice proper form

If you are an active individual, it would not hurt to consult with a physical therapist or strength and conditioning specialist to ensure that you are practicing proper form in your movements. For example, if you are squatting, are your knees jetting far over your toes? Or are you sitting back far enough so your knees stay over toes? When your body is in proper form, your body is moving properly and you can avoid injury! It's when we deter from proper form that problems arise.

3) Maintain proper mobility of the hip and IT band

The IT band, also known as the iliotibial band/tract, lies to the outside of your leg. When the IT band is not properly stretched, thus not maintaining proper mobility, there is a chance the kneecap can be pulled out of it's proper position externally.

Think you may have experienced a patella dislocation? Seek the attention of a medical professional to find out what may have caused the dislocation. They may order an x-ray or MRI depending on the severity of the dislocation to ensure that other structures of the leg were not compromised.

Take action to find out what you should be doing to avoid a patella dislocation!

#patella #patelladislocation #injuryprevention

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