Overview
A patella fracture is a break in the kneecap (the patella), one of the main bones that helps you straighten your knee. The fracture can interfere with the extensor mechanism, which involves the quadriceps tendon, the patella, and the patellar tendon working together to help you stand and walk. Pain, swelling, and stiffness are common because the area is highly sensitive and moves every time the knee bends. Some patella fractures are stable and can heal without surgery, especially when the kneecap pieces are well aligned.
Symptoms
You typically feel pain in the front of the knee after a direct blow or a fall, and swelling may appear quickly. Bruising is common, and bending or straightening the knee can be very painful. If the fracture affects the extensor mechanism, you may have trouble fully straightening the knee or performing a straight-leg raise. Walking may feel unsafe, and you may need to limit weight-bearing until pain and stability improve.
Causes
Patella fractures most often result from a direct impact to the front of the knee or from a sudden forceful contraction of the quadriceps. They can also occur from twisting injuries or falls, especially in older adults with weaker bones. The kneecap is under significant stress during knee extension, so alignment and tendon function strongly influence how the injury presents and heals.
Risk Factors
Risk increases with activities that involve falls or direct knee trauma, such as sports with contact, climbing, or working in environments with hard surfaces. Older age, osteoporosis, and long-term corticosteroid use can make fractures more likely after relatively minor impacts. In some people, prior knee injuries or reduced strength around the hips and thighs may contribute to loss of control during falls.
Prevention
You can reduce risk by improving fall prevention, including good lighting, removing loose rugs, and using appropriate footwear. Strengthening the quadriceps, hips, and core can improve knee stability and help protect the leg during slips or stumbles. If you have osteoporosis or low bone density, managing bone health with your clinician and using protective strategies during higher-risk activities can lower fracture risk.
How the Diagnosis Is Evaluated
Clinicians usually start with a detailed history about how the injury happened and a physical exam focused on tenderness over the kneecap, swelling, bruising, and knee alignment. They often check whether you can fully straighten the knee and perform a straight-leg raise, which helps assess whether the extensor mechanism is functioning. Imaging typically begins with X-rays, and a CT scan may be used when fracture pattern details are unclear or when alignment matters for treatment planning. If tendon or cartilage injury is suspected, MRI may be considered, but not every patient needs advanced imaging.
Nonsurgical Treatment Options
Non-surgical care is commonly used when the fracture is non-displaced or stable and the extensor mechanism remains intact. Treatment typically includes immobilization with a knee brace or immobilizer, followed by gradual, guided range-of-motion and strengthening through physical therapy. Pain control may involve ice, elevation, and medications such as acetaminophen or NSAIDs if they are safe for you. Your clinician may recommend a protected weight-bearing plan and activity restrictions to avoid stressing the fracture while it heals. Follow-up exams and repeat imaging are often used to confirm that the kneecap stays aligned during recovery.
When to Seek Medical Attention
Seek urgent medical attention if you cannot bear weight, you have a deformity of the kneecap, or you suspect the kneecap is "out of place." Go promptly if you cannot straighten your knee or perform a straight-leg raise, because this can indicate extensor mechanism involvement. Get immediate care for severe, rapidly worsening swelling, fever, open wounds over the injury, or numbness/tingling that is progressing. If your symptoms do not start to improve within a few days, or if pain and swelling significantly increase, you should be re-evaluated.
Frequently Asked Questions
Healing often takes several weeks, but full recovery can take longer depending on fracture stability and how well motion and strength return.
Difficulty straightening the knee or inability to do a straight-leg raise may suggest extensor mechanism dysfunction and should be evaluated promptly.
Next Steps
If you suspect a kneecap fracture, it's important to get evaluated promptly so alignment and extensor mechanism function can be assessed. Follow your clinician's guidance on bracing, weight-bearing, and physical therapy progression, and seek re-evaluation if pain, swelling, or function worsens.