What a Fractured Kneecap Looks Like

By Your Health Magazine Health Information Team

You fall directly onto your knee, hear or feel a hard impact, and within minutes the area becomes painful and swollen. Looking down, you may wonder: What does a fractured knee look like, and can you tell the difference between a broken bone and a severe bruise?

A fractured kneecap does not always have an unmistakable appearance. Some fractures cause dramatic swelling or deformity, while a small, stable crack may leave the knee looking bruised but otherwise normal. Because appearance alone cannot confirm or rule out a fracture, significant pain or loss of function after a knee injury should be medically evaluated.

What Does a Fractured Knee Look Like?

People often use “fractured knee” to describe any broken bone around the knee joint. Fractures in the knee may involve the lower end of the thighbone, the upper end of the shinbone or the patella—the small bone commonly called the kneecap. A fractured kneecap usually causes changes centered at the front of the knee.

Depending on the severity of the injury, the knee may have:

Rapid or pronounced swelling around the kneecap
Blue, purple, red or yellow bruising
Scrapes, cuts or other skin damage from the impact
An unusually shaped, flattened or uneven-looking kneecap
A visible or noticeable gap between separated bone fragments
Bleeding or bone visible through a wound in an open fracture

Not every broken kneecap looks deformed. With a nondisplaced fracture, the pieces remain in their normal position, so the outside of the knee may show only swelling and bruising. A displaced fracture can create a more obvious change because the broken pieces have moved apart. In a comminuted fracture, the patella has broken into several pieces, often after a forceful direct impact.

What Does a Broken Kneecap Feel Like?

The way the knee functions can be as important as its appearance. The patella is part of the knee’s extensor mechanism, which connects the quadriceps muscle in the thigh to the patellar tendon below the knee. This system allows you to straighten the leg, stand, walk and climb stairs.

Common symptoms of a patellar fracture include:

Immediate pain at the front of the knee
Tenderness directly over the kneecap
Pain that becomes worse with movement or pressure
Difficulty bending or straightening the knee
Inability to lift the straightened leg off a bed or floor
Difficulty standing, walking or putting weight on the injured leg
A grinding sensation or the feeling that the kneecap is unstable

Swelling can be substantial because bleeding may collect inside the knee joint. However, the ability to walk does not prove that the bone is intact. Some people can place weight on a leg with a stable fracture, although doing so may be painful and could worsen an unstable injury.

Other knee injuries, including a kneecap dislocation, tendon rupture or severe soft-tissue contusion, can produce similar symptoms. For a closer review of warning signs, read about symptoms that may occur with a fractured knee.

What a Kneecap Fracture Looks Like on an X-Ray

A healthcare professional generally uses X-rays to determine whether the patella is broken and whether the fragments remain properly aligned. On an X-ray, what does a broken kneecap look like? Its appearance depends on the fracture pattern:

A nondisplaced fracture may appear as a thin crack while the bone retains its usual shape.
A transverse fracture creates a line across the kneecap, sometimes separating it into upper and lower pieces.
A vertical fracture runs from the upper portion of the patella toward the lower portion.
A displaced fracture shows a space or misalignment between fragments.
A comminuted fracture produces multiple irregular fragments and may resemble a shattered or star-shaped break.

Several X-ray views may be needed because the kneecap overlaps other knee structures from certain angles. Computed tomography may be used when a fracture is complex or its full pattern is unclear. The physical examination is also important because imaging must be considered together with the person’s ability to straighten the knee and the condition of the surrounding skin, tendons, nerves and circulation.

How Kneecap Fractures Commonly Happen

Most patellar fractures result from a direct blow, such as falling onto a hard surface, striking the dashboard during a vehicle collision or receiving a forceful hit during sports. Less commonly, a powerful and sudden contraction of the quadriceps muscle can pull the patella apart.

Low bone density may make a bone more vulnerable to breaking, but a healthy kneecap can also fracture when the force is strong enough. General information about bone, joint and injury conditions is available through the MedlinePlus health topics collection.

How a Fractured Kneecap Affects Everyday Life

A kneecap fracture can make routine activities difficult, including getting out of a chair, entering a car, using stairs and walking to the bathroom. Early treatment often involves keeping the knee straight in a splint, cast or brace. Crutches or another walking aid may be needed, depending on the injury and weight-bearing instructions.

Stable fractures with little or no displacement may heal without surgery when the knee’s extensor mechanism remains intact. More serious injuries may require surgery to realign and secure the fragments with screws, wires, pins or plates. Open fractures, widely separated pieces and injuries that prevent active knee extension are among the situations more likely to need an operation.

Rehabilitation is an important part of recovery. Immobilization protects the healing bone, but it can also contribute to knee stiffness and weakness in the thigh muscles. Physical therapy may gradually restore motion, strength and walking ability when the fracture is stable enough. Recovery time varies according to the fracture pattern, associated injuries, treatment and overall health.

When to Seek Care

Seek prompt evaluation after a forceful knee injury if there is significant swelling, severe pain, difficulty bearing weight or an inability to bend or straighten the leg. An urgent care clinic, emergency department, primary care professional or sports medicine clinician can perform an initial assessment and arrange imaging.

Emergency care is appropriate if the knee is visibly deformed, bone is exposed, a wound lies over the suspected fracture, or the foot becomes numb, pale, blue or cold. While waiting for care, limit movement and avoid trying to straighten a deformed knee or push exposed bone back into place. An orthopedic surgeon may be consulted when the fracture is displaced, open, complex or affecting the knee’s extensor mechanism.

The Bottom Line

A fractured kneecap may look swollen, bruised, scraped or misshapen, but it may also resemble an ordinary knee injury. The most concerning clues include intense pain over the kneecap, rapid swelling, a noticeable gap or deformity, and an inability to straighten the leg or walk. Only a clinical examination and appropriate imaging can determine whether the patella is broken and what treatment may be needed.