Knee Fracture
A break in one of the bones forming the knee joint
Quick Facts
- Type: Bone fracture (orthopedic injury)
- Bones involved: Patella, tibia, or femur at the knee
- Common cause: Falls, direct blows, vehicle crashes
- Treatment: Immobilization or surgery
Overview
A knee fracture is a break in any of the bones that form the knee joint: the kneecap (patella), the top of the shinbone (tibial plateau), or the lower end of the thighbone (distal femur). Because the knee bears the body's weight and is essential for walking, a fracture here can significantly affect movement and may need careful treatment to restore a smooth joint surface.
Knee fractures range from a simple, stable crack to a shattered (comminuted) break or a fracture that breaks through the skin (open fracture). The treatment and recovery depend heavily on which bone is broken, how the pieces are positioned, and whether the joint surface is involved.
Symptoms
Symptoms of a knee fracture usually appear right after the injury:
- Severe pain in or around the knee
- Marked swelling and bruising
- Inability to bear weight or straighten the leg
- Visible deformity or the kneecap sitting out of place
- Tenderness directly over the broken bone
An open fracture, in which bone breaks through the skin, or signs of poor blood flow such as a cold, pale, or numb lower leg, are emergencies that require immediate care.
Causes
Knee fractures generally result from significant force:
- Falling directly onto the knee
- A direct blow, such as a dashboard injury in a car crash
- Sports collisions or twisting injuries
- Landing hard from a height
In people with weakened bones from osteoporosis, a lower-energy fall can be enough to cause a fracture. A sudden, forceful contraction of the thigh muscle can also pull the kneecap apart.
Risk Factors
- Osteoporosis or other conditions that weaken bone
- Older age and a higher risk of falls
- High-impact sports and activities
- Motor vehicle use and occupations with fall hazards
- Previous knee injury or surgery
Diagnosis
Diagnosis combines an examination with imaging:
- X-rays: The main test to confirm a fracture and show its pattern and position.
- CT scan: Provides detailed views of complex breaks, especially those involving the joint surface, to guide surgery.
- MRI: May be used to assess associated ligament, cartilage, or soft-tissue injuries.
The clinician also checks circulation, sensation, and movement in the lower leg and foot.
Treatment
Treatment depends on which bone is broken and whether the pieces are displaced.
- Nonsurgical care: Stable fractures that remain in good position may be treated with a cast, brace, or splint, keeping the leg still while the bone heals.
- Surgery: Displaced fractures, broken joint surfaces, or open fractures usually require surgery with plates, screws, or wires to realign and hold the bone.
- Pain control and rehabilitation: After the bone is stabilized, physical therapy gradually restores motion, strength, and walking ability.
Healing typically takes several weeks to a few months, with rehabilitation continuing beyond that.
Prevention
- Keep bones strong with adequate calcium, vitamin D, and weight-bearing exercise
- Have bone density checked if you are at risk for osteoporosis
- Reduce fall hazards at home, such as loose rugs and poor lighting
- Wear seat belts and use protective gear in sports
- Use proper footwear and assistive devices if balance is a concern
When to See a Doctor
Seek emergency care after a knee injury if you cannot bear weight or straighten the leg, the knee is severely deformed, bone is visible through the skin, or you have a cold, pale, numb, or pulseless foot. Severe pain, rapid swelling, or an inability to use the leg also warrant prompt evaluation, since a missed or untreated fracture can lead to lasting joint problems.
Frequently Asked Questions
How do I know if my knee is broken or just bruised?
Both can cause pain and swelling, but a fracture often makes it impossible to bear weight or straighten the leg and may cause deformity. Only an X-ray can confirm whether a bone is broken, so seek evaluation if you cannot use the leg or the pain is severe.
Does a broken kneecap always need surgery?
No. A kneecap fracture that stays in good position and lets you straighten your leg can sometimes heal in a cast or brace. Surgery is needed when the pieces are separated or the joint surface is disrupted.
How long does a knee fracture take to heal?
Most knee fractures take several weeks to a few months to heal, depending on the bone, the severity, and whether surgery was needed. Physical therapy afterward is important to regain motion and strength.
When is a knee fracture an emergency?
Bone breaking through the skin, severe deformity, or a cold, pale, numb, or pulseless foot are emergencies and require immediate care. These can signal an open fracture or injury to nerves or blood vessels.
References
- American Academy of Orthopaedic Surgeons (OrthoInfo). Patellar (Kneecap) Fractures.
- Mayo Clinic. Broken bones (fractures).
- MedlinePlus, U.S. National Library of Medicine. Fractures.
- StatPearls, National Library of Medicine. Tibial Plateau Fractures.