Why My Knee Popped Out of Place, Then Right Back in Again

What Is Patellar Instability?

Patellar instability is a condition in which your kneecap slides or moves out of its normal position within your trochlear groove, which is the groove on the femur that your kneecap sits on. This groove helps to stabilize your kneecap and keep it from sliding.

However, if you have patellar instability, the movement will result in an unstable kneecap and can even lead to a dislocated kneecap. The instability of your patellar may be classified as acute or chronic, depending on how frequently it occurs.

Acute instances generally occur in sports, specifically football, basketball, and volleyball. Young athletes whose ages range from 13-20 have the highest incidence rates. Additionally, due to anatomic issues, teenage females are at the highest risk of experiencing instability.

What Happens When My Knee “Pops” Out of Place?

You may wonder what happens when your knee “pops” out of place. Two things can happen. When your knee “pops” out of place, your patella may be “subluxated” or “dislocated,” depending on the degree of your patella instability.

A subluxation is a partial knee dislocation and occurs when your kneecap slightly shifts out of the groove and then “pops” back into place. A patella dislocation occurs if your patella moves entirely out of the groove and stays in that position.

Generally, when you bend or straighten your leg, your kneecap will move up and down in your trochlea groove on the thigh bone. When it comes to patellar instability, your kneecap does not track the groove properly.

What Causes a Kneecap Dislocation to Happen?

The most common cause of a kneecap dislocation is a non-contact twisting injury when the knee joint is almost fully extended. Additionally, a direct blow to the kneecap while playing sports, a fall, or another form of accident can cause a partial or complete dislocation.

During such injuries, the medial patellofemoral ligament (MPFL) can become damaged. This ligament plays an important role in kneecap stability.

Who is at Risk for Kneecap Dislocation and Subluxation?

Kneecap dislocation and subluxation are more common in young women, especially those with “loose” or hypermobile joints. Female athletes in high-impact sports like soccer and basketball are particularly at risk due to the physical demands of these activities. Though less common, men and boys can also experience patellar instability.

Risk factors include:

• Shallow Trochlear Groove: A less-defined groove provides less stability, allowing the kneecap to dislocate more easily.
• Abnormal Patellar Tendon Alignment: When the tendon attaches abnormally on the shin, it can misalign the kneecap.
• Knock Knees (Genu Valgum): Inward-angled knees add strain to the patella.
• High-Riding Kneecap (Patella Alta): A higher position on the thigh bone leaves the kneecap less supported.

These anatomical traits make it easier for the kneecap to shift or dislocate, especially during twisting, jumping, or direct impact activities.

Dislocated Knee Symptoms

If you have a dislocated knee, you may experience the following:

• Severe pain
• Swelling
• Visible deformity
• Decreased range of motion (ROM)
• Tenderness in the area
• “Popping” sounds when you bend your knee or climb stairs

How Can a Dislocated Knee Be Diagnosed?

To ensure that an accurate diagnosis is made, your specialist will first review your medical history. They will also perform an apprehension test to assess your injury. Imaging tests, such as an X-ray, may also be ordered to provide your specialist with a diagnostic view to ensure that your patella has not been fractured.

It is important to note that even if your knee cap moves back into place on its own, you should still seek the assistance of a specialist so that they can accurately provide a diagnosis and treatment if needed. They can also verify that the surrounding muscles, ligaments, nerves, and blood vessels have not been injured.

Treatment Options for a Dislocated Knee

Because each circumstance and injury will vary, your orthopedic surgeon will determine whether non-surgical or surgical intervention is the best treatment for your knee pain.

The initial management of your injury may include swelling reduction, bracing to immobilize your knee joint, and possibly using crutches to assist in weight-bearing so that your knee will not buckle.

Additionally, physical therapy can also be beneficial to your recovery because it strengthens the muscles that hold your kneecap in place. During your physical therapy sessions, a physical therapist will also assist you in improving your range of motion.

If you have chronic patellar instability or a complete kneecap dislocation, your specialist may recommend surgery.

How Can I Prevent Patellar Dislocation From Reoccurring?

Naturally, you may wonder how to prevent patellar dislocation from reoccurring. Below, you will find some helpful tips to guide you in preventing this from becoming a recurring event.

Helpful Strategies to Decrease the Recurrence of Knee Dislocation:

• Modifying your activities
• Stretching
• Quad-strengthening to keep your thigh muscles strong
• Using a knee brace
• Using custom orthotics
• Maintaining a healthy weight

A dislocated knee, whether partial or complete, can be extremely painful. Schedule an appointment with one of our board-certified knee specialists at OrthoNeuro today to get relief from your knee injuries! 

We have many offices throughout Columbus, Ohio, for your convenience. Let us provide you with the relief you deserve!