Knee Fracture

First aid for a suspected knee fracture

1. Keep the leg still and support it in the position found. Do not try to straighten a deformed knee.
2. Apply ice wrapped in a cloth, for up to 20 minutes.
3. Raise the leg gently if possible.
4. Cover open wounds with a clean dressing.
5. Do not walk on it. Get to an ER or urgent care, or call 911 for severe injuries.

Types of knee fracture

Kneecap (patella) fractures

The kneecap sits in front of the knee within the quadriceps tendon. It breaks from direct falls onto the knee or, less often, from a violent quadriceps contraction. Types include non-displaced, transverse, comminuted (shattered) and vertical fractures. A key test is whether you can raise the straight leg: if not, the extensor mechanism is disrupted and surgery is usually needed. See patellar fracture.

Tibial plateau fractures

These involve the flat top of the shin bone that forms the knee joint surface. They result from high-energy crashes in younger people and simple falls in older adults with weak bones. They often damage the cartilage, ligaments and meniscus, and the joint surface must be restored as level as possible.

Distal femur fractures

Breaks at the lower end of the thigh bone, just above the knee, from major trauma in younger people or falls in older adults, especially those with osteoporosis or knee replacements (periprosthetic fractures). See femur fracture.

Other fractures around the knee

• avulsion fractures, where a ligament or tendon pulls off a bone fragment, such as a tibial spine fracture with ACL injury in children
• osteochondral fractures, chips of cartilage and bone, often with kneecap dislocation
• fibular head fractures, which can injure the peroneal nerve, causing foot drop

Symptoms

• severe pain at the time of injury
• swelling within hours, often from blood in the joint (hemarthrosis)
• bruising
• inability to bear weight or straighten the knee
• a visible deformity or palpable gap in the kneecap
• numbness or tingling in the foot if nerves are affected

Knee fracture vs sprain

The Ottawa knee rules

Doctors order a knee X-ray after injury if any of the following apply:

• age 55 or older
• tenderness at the head of the fibula
• isolated tenderness of the kneecap
• inability to bend the knee to 90 degrees
• inability to bear weight for 4 steps, both immediately and in the clinic

Diagnosis

• X-rays from several angles confirm most fractures.
• CT scan shows the fracture pattern and joint surface, especially for tibial plateau and distal femur fractures.
• MRI detects ligament, meniscus and cartilage injuries and hidden fractures.
• Vascular studies if pulses are abnormal, because knee injuries can damage the popliteal artery.

Treatment

Non-surgical

Suitable for non-displaced, stable fractures with an intact extensor mechanism:

• a hinged knee brace or cylinder cast, often locked straight at first
• crutches with limited weight-bearing for several weeks
• pain relief and ice
• gradual range-of-motion exercises guided by the surgeon

Surgical

Recommended for displaced fractures, joint surface step-offs, open fractures and those preventing knee straightening:

• patella: tension band wiring, screws or plates. Badly shattered fragments may be removed
• tibial plateau: plates and screws to restore the joint surface, sometimes with bone graft. Severe injuries may first need an external fixator while swelling settles
• distal femur: plates or an intramedullary nail. Knee replacement is an option for some older adults with very poor bone
• repair of associated ligament or meniscus injuries

Recovery

Physical therapy is essential to restore motion and quadriceps strength. Stiffness is the most common problem after knee fractures.

Complications

• knee stiffness and loss of motion
• post-traumatic arthritis, especially after joint surface fractures
• blood clots in the leg
• infection after surgery or open fractures
• compartment syndrome, most often after tibial plateau fractures
• hardware irritation, sometimes requiring removal
• nonunion or malunion
• nerve or artery injury

Frequently asked questions

What are the signs of a broken knee?

Signs include severe pain, rapid swelling, bruising, inability to bear weight or straighten the leg, tenderness over a bone, and sometimes a visible deformity or gap in the kneecap. An X-ray is needed to confirm a fracture.

Can you walk on a fractured knee?

Sometimes, with a small non-displaced fracture, but it is usually very painful and can make the fracture worse. Most people with a knee fracture cannot take more than a few steps. Keep weight off it until it has been assessed.

How long does a knee fracture take to heal?

The bone typically heals in 6 to 12 weeks. Return to daily activities usually takes 3 to 4 months, and full recovery including sports or heavy work can take 6 to 12 months, depending on the fracture type and treatment.

Does a broken kneecap need surgery?

Not always. Non-displaced fractures where you can still raise your straight leg are often treated with a brace. Displaced fractures, or those that prevent straightening the knee, usually need surgery to restore the kneecap and the quadriceps mechanism.

Can a knee fracture cause arthritis later?

Yes. Fractures that involve the joint surface, especially tibial plateau fractures, increase the risk of post-traumatic arthritis years later. Restoring a smooth joint surface and maintaining strength and a healthy weight help reduce this risk.