Can you break your knee cap and not know it?

Written By on September 24, 2021 — Medically Reviewed By Kris Ceniza (PT)

Written by on September 24, 2021 — Medically Reviewed By: Kris Ceniza (PT)

People fall on their knees pretty often. And, kneecap fractures can happen because of them. So, you might be wondering, can you break your knee cap and not know it?

The short answer is: It’s unlikely. Fractures tend to be very painful. Plus, there might be other glaring symptoms. But, there could also be times where you might not notice a patellar fracture. This depends on the type of fracture or if you have certain medical conditions.

I’ll walk you through them all in a bit but I’ll also discuss the following:

  • How to identify a knee cap fracture,
  • How to treat it, and
  • Its average recovery time

For now, let’s get to the main topic:

Can you have a kneecap fracture and not know it?

It’s unlikely. Kneecap fractures often happen after (1):

  • You fall on your knees.
  • A direct blow to your kneecap.
  • Landing with your knees straight.

An example of a direct blow would be if you get in a car accident. The impact forces your knee to hit the dash, possibly resulting in a fractured kneecap.

Conversely, landing with straight knees might also force your knees to bend on impact. This, in turn, results in a sudden stretch to your quadriceps muscles, causing the fracture.

Ultimately, there’s almost always a traumatic event before fractures. This tends to cause bruising, swelling, and pain.

Speaking of pain…

As a rule, most fractures hurt – and they hurt bad.

Severe pain is the most effective way to let you know you need help A.S.A.P.

Knee Force Knee Sleeve

For a patella fracture, you likely won’t also be able to walk or straighten your knee. Along with pain, these symptoms help you avoid making the injury worse.

But, most rules also have exceptions. This included.

You may not notice a kneecap fracture if…

It’s an incomplete fracture

In other words, your bone cracked but didn’t break into separate pieces. This can happen after falling onto your knees, for example.

This type can look like any other fresh injury. The pain and swelling can be mild. You might even be able to walk, bend your leg, and keep your knee straight.

You have a medical condition that impairs your pain levels

Some health issues change your pain perception. So, a fracture may go unnoticed unless there’s an obvious deformity or severe symptoms.

Some of these conditions include:


People with fibromyalgia are unable to process pain the way healthy people do. Research even says that patients with this disease perceive pain to a lesser degree. (2)

Thus, pain from a non-displaced fracture can go unnoticed.

Peripheral diabetic neuropathy

This is the damage of the nerves on the arms and/or legs due to diabetes. Thus, compromising pain perception.

This info is crucial since 50-66% of diabetes patients develop this at some point. (3)

Congenital insensitivity to pain

This is a rare disease where the person can’t feel pain. This means they won’t notice a fracture, regardless of its severity.

The lack of sensitivity to pain makes it harder to heal the injury as well. And, people with this condition are more prone to infections and other health issues. (4)

How do you know if you have a patella fracture?

The patella is the triangular bone at the front of the knee. It glides up and down the thigh bone every time we walk or climb stairs.

The kneecap connects to the shin bone through the patellar tendon. This makes it possible for us to straighten our knee joints.

If the kneecap breaks, your symptoms may worsen when you straighten or bend your knee. For example (1):

  • Standing and/or walking can be very painful.
  • It can be hard or impossible to raise your leg straight.
  • In displaced fractures, the knee will look deformed.
  • You may have swelling and bruising in the area.

Types of patellar fractures


Here, the broken pieces are in still their original position, or their separation is <3mm.

Treatment doesn’t include surgery unless (5):

  • The fragments move out of place, or
  • If it’s a comminuted fracture

It’s a comminuted fracture if there are 3 or more bone fragments.

More than half of comminuted fractures are non-displaced. But, they often involve severe damage to the surrounding tissues. So, full recovery might warrant surgery. (5)


Here, the broken pieces have a separation of >4mm. Again, it can happen after a car accident if your knee hits the dashboard.

Most cases may need surgery to ensure proper healing. (5)

Knee Force Knee Sleeve

Open fractures also need surgery.

Open fractures are when the fractured bone pierces the skin.

This is a type of displaced fracture that’s also considered a medical emergency.

It has a high risk of complications, including non-union and infection. (5)

Treatment of kneecap fractures

The treatment will depend on the type of fracture.

If it’s an open fracture, you’ll likely go straight to the OR. If it’s a closed fracture, your doctor will (5):

  • Request an x-ray to see the severity of the damage.
  • Ask you to straighten your knee and raise it. This could rule out severe surrounding damage.
  • See you standing onto your knee. This can help them decide whether you’re allowed to walk.

After this, your doctor will know which treatment will be best for you. Your treatment will include one or more of the following:

Wear a cast or splint

You may have to wear this during the first 1-3 weeks of recovery. It will keep the bone fragments in their place. You may have to walk with crutches during that time, though. (5)

Afterward, your doctor may replace the cast with a knee brace. A knee brace can aid recovery, help you walk again, and protect the area at the same time.

Physical therapy

Physical therapy is key to full recovery after a patella fracture.

Prolonged immobilization can cause nonunion of the bones. And, in turn, trigger chronic knee pain and other complications.

PTs help you regain your knee range of motion. They use safe stretches and exercises that don’t move your bone pieces out of place. (1)

Knee joint surgery

Orthopaedic surgeons often fix a patella fracture with screws or sutures. The surgical technique and recovery time will depend on the severity of the injury.

You may have to wear a cast, knee brace, and/or crutches afterward. You’ll also need to undergo PT rehabilitation.

How long does it take to recover from a patellar fracture?

It typically takes at least 8 weeks to heal. It will take more depending on (1):

  • Whether you’re adhering to the treatment or not. Non-compliant patients take longer to heal.
  • The diagnosis and the level of damage. Open fractures need more time, compared to closed ones.
  • The surgical repair technique.
  • Any previous health issues you may have. For example, people with diabetes may take longer to recover.


Can you walk on a fractured knee cap?

Walking may be safe if you can perform a straight leg raise. In this case, your doctor can suggest walking with partial weight-bearing.

But, keep in mind that walking can worsen some fractures. Talk to your doctor before doing any physical activity.

What happens if you leave a broken knee untreated?

The fracture may not heal properly. Thus, the pain and swelling may remain over time. This can cause chronic pain, which is very difficult to overcome.

Untreated bone fragments can also damage surrounding tissues. Like muscles, tendons, or nerves. This will make recovery harder.

What is the average healing time of a broken patella?

8-12 weeks. This is with conservative treatment and 100% compliance from the patient. (1)

Conclusion: Can you have a patella fracture without knowing?

It’s unlikely. Most patella fractures are painful. They also cause swelling and can make it hard for you to move your knee.

But, an incomplete fracture may go unnoticed for some people. Also, people with impaired pain perception may not know they have a fracture.

Whichever the case, please go to the doctor if both of these are true:

  • You had a traumatic event on your knee.
  • The symptoms aren’t improving after 72 hours.

The doctors will rule out a fracture, tear, or other injuries.


  1. Gwinner, Clemens et al. “Current concepts review: Fractures of the patella.” GMS Interdisciplinary plastic and reconstructive surgery DGPW. Jan. 2016. DOI: 10.3205/iprs000080
  2. Bhargava J, Hurley JA. “Fibromyalgia.” [Updated 2021 Jul 25]. StatPearls. Retrieved on September, 2021 from:
  3. Bodman MA, Varacallo M. “Peripheral Diabetic Neuropathy.” [Updated 2021 Jul 26]. StatPearls. Retrieved on September, 2021 from:
  4. Schon, KR et al. Congenital Insensitivity to Pain Overview.” [Updated 2020 Jun 11]. GeneReviews. Retrieved on September, 2021 from:
  5. Melvin, J et al. “Patellar fractures in adults.” Journal of the American Academy of Orthopaedic Surgeons. (2011). DOI: 10.5435/00124635-201104000-00004
Mitch Torres (PT)
Mitch is a physical therapist, personal trainer, and nutrition coach. Fascinated with the knee joint, Mitch poured that passion into writing about knee pain and how to overcome it with movement. His goal is to teach you how to apply this knowledge into your daily life, so you can keep knee pain away for good.