Knee Fracture 

Updated: Oct 17, 2015
Author: Mark Steele, MD; Chief Editor: Trevor John Mills, MD, MPH 



Fractures of the knee include fractures of the patella, femoral condyles, tibial eminence, tibial tuberosity, and tibial plateau.[1, 2] Direct and indirect forces can cause these fractures.


Patellar and tibial plateau fractures each account for 1% of all skeletal fractures. Distal femoral condyle fractures account for 4% of all femur fractures. Fractures of the knee can result in neurovascular compromise or compartment syndrome, with resultant risk of limb loss.[2] Soft-tissue infection or osteomyelitis can occur with open fractures. Other complications include nonunion, delayed union, osteoarthritis, avascular necrosis, fat embolism, and thrombophlebitis.




Patients with knee fractures may have a history of the following:

  • Direct or indirect trauma with resultant pain and edema

  • Patella fracture - Caused by a direct blow, such as a dashboard injury in a motor vehicle accident or a fall on a flexed knee, also caused by forceful quadriceps contraction while the knee is in the semiflexed position (eg, in a stumble or fall)

  • Femoral condyle fractures due to axial loading with valgus or varus stress

  • Tibial eminence fracture[1] - Due to a direct blow to the proximal tibia with the knee flexed such as falling off a bicycle, also due to hyperextension with varus or valgus stress, such as in motor vehicle collisions or athletic accidents[3] (Tibial eminence avulsion fractures occur most often in children aged 8-14 years but can also occur in the skeletally mature patient.[1] )

  • Tibial tubercle fracture - Usually occur with jumping activities such as basketball, diving, gymnastics, and football[3] , more common in males than in females, more common in adolescents; infrequent in adults

  • Tibial plateau fracture - Caused by axial loading with valgus or varus forces, such as in a fall from a height or collision with the bumper of a car, due to the impaction of the femoral condyle into the tibial plateau (In elderly persons and those with osteoporosis, tibial plateau fracture can occur with minor trauma. Patient is generally unable to bear weight. The lateral tibial plateau is fractured more frequently than the medial plateau.)


When examining a patient for a knee fracture, one should first examine the patient for edema, ecchymosis, and point tenderness. A careful neurovascular examination should be performed. Ask the patient to perform a straight-leg raise against gravity to check the integrity of the extensor mechanism, which commonly is disrupted with transverse patellar fractures caused by indirect forces.[2]

Patella fractures

Patients present with pain directly over the patella.

The patient may have pain with leg extension or be unable to extend the knee with a severe fracture.

Femoral condyle fractures

Patient will present with pain over the distal femur and often will have a hemarthrosis.

Patients are often unable to bear weight.

Femoral condyle insufficiency fractures are frequently associated with overlying cartilage loss and ipsilateral meniscal injury. The extent of cartilage loss and meniscal damage, in addition to loss of knee range of motion at the time of presentation, are significantly associated with clinical progression.[4]

Tibial eminence fractures

Patients may present with a knee effusion and pain.[1]

Patients may represent with an avulsion of the tibial attachment of the anterior cruciate ligament.

Tibial tubercle fractures

Patients present with pain over the anterior tibia about 3 cm distal to the articular surface.

In severe fractures, the patient may be unable to extend the knee.

Tibial plateau fractures

Often, patients present with a knee effusion, and tenderness will be present over the medial or lateral plateau.

Up to 30% of tibial plateau fractures are associated with knee ligamentous injuries (medial collateral or anterior cruciate ligaments with lateral plateau fractures, lateral collateral or posterior cruciate ligaments with medial plateau fractures).


Knee fractures may be caused by the following:

  • Trauma (direct or indirect)

  • Chronic stress

  • Pathologic conditions





Imaging Studies


Obtain anteroposterior, lateral, and oblique radiographs of the knee.[5] Four views have been shown to be superior to two views in detecting fractures.[6]

Oblique views are particularly useful in detecting subtle tibial plateau fractures (internal oblique profiles lateral plateau, external oblique profiles medial plateau). Oblique views also better identify obliquely oriented femoral condyle fractures.

An axial (or sunrise) view of the patella is useful for detecting vertical patellar fractures, which frequently are missed and nondisplaced. Transverse fractures are most common, followed by comminuted and avulsion-fractures. Adding a sunrise view increases the negative predictive value of radiographs for ruling out patellar fracture.

A fat-fluid level (lipohemarthrosis) may be identified on a lateral view of the knee; this finding indicates an intra-articular fracture.

Radiographic evidence of ligamentous injury may be present:

  • An avulsion fracture at the site of attachment of the lateral capsular ligament on the lateral tibial condyle (Segond fracture) is a marker for anterior cruciate ligament rupture.[7]

  • Cortical avulsion fracture of medial tibial plateau (uncommon) is associated with tears of the posterior cruciate ligament and medial meniscus.[8]

A patellar spur at the superior portion of the patella is associated with a ruptured quadriceps tendon.[9]

Use of the Ottawa rules for obtaining knee radiographs have proven sensitive for fracture and have reduced ED waiting times and costs.[10] The rules include the following patient findings:[11]

  • Age 55 years or older

  • Tenderness at head of fibula

  • Isolated tenderness of patella

  • Inability to flex knee to 90 degrees

  • Inability to bear weight (4 steps) immediately after injury and in ED

CT scans and MRIs

CT scans may be necessary to fully delineate the extent of tibial plateau fractures and other complex knee fractures.

Computed tomography can be a useful diagnostic modality in preoperative planning for tibial plateau fractures. Tibial plateau fracture maps in one study showed recurrent patterns of fracture lines, revealing 4 major fracture characteristics: the lateral split fragment, found in 75%; the posteromedial fragment, seen in 43%; the tibial tubercle fragment, seen in 16%; and a zone of comminution that included the tibial spine and frequently extended to the lateral condyle, seen in 28%.[12]

Compared to CT scans, plain radiography underestimates the amount of articular depression of tibial plateau fractures in most tibial regions. This is significant as the amount of tibial plateau depression is an indicator for operative repair.[13]

CT scans are also useful in severely injured patients when obtaining radiographs in all angles is difficult.

MRIs also are useful and have the added benefit of depicting associated soft-tissue (eg, ligamentous, meniscal) injury.[14]


Arthrocentesis may be of diagnostic and therapeutic benefit for tense effusions. Presence of blood and glistening fat globules indicates lipohemarthrosis, which is pathognomonic for intraarticular knee fracture.



Prehospital Care

Document the neurovascular status. Apply a sterile dressing to open wounds.

Splint the injury.

Administer parenteral analgesics for isolated extremity injury.

Emergency Department Care

Care for various fractures is as follows:[15, 16, 17]

Patella fracture

Nondisplaced transverse fractures with an intact extensor mechanism are treated with a knee immobilizer, crutches, restriction to only partial weight bearing, and 6 weeks of immobilization.

Displaced fractures, or fractures associated with a disrupted extensor mechanism, are referred to orthopedics for possible open reduction and internal fixation. A partial or total patellectomy may be required for severe comminution.

Patients with open fractures should receive antibiotics and orthopedics should be consulted for emergency irrigation and debridement.

Femoral condyle fracture

These may be supracondylar, intercondylar, or condylar.

Due to the proximity of the neurovascular structures, a thorough neurovascular examination must be obtained.

Obtain an orthopedic consult. Nonoperative management may be used for nondisplaced or incomplete fractures. Open fractures, displaced fractures, and those with neurovascular injury will need operative fixation.[16]

Tibial spine fracture

For a nondisplaced fracture (and stable knee joint), immobilize the knee.

Obtain an orthopedic consultation for an unstable knee, a complete avulsion of the tibial spine, or a displaced fracture for possible surgical fixation.

Tibial tubercle fracture

For nondisplaced fractures, immobilize the knee.

Obtain an orthopedic consultation for displaced fracture to consider open reduction and internal fixation.

Tibial plateau fracture

Immobilize nondisplaced fractures and have patient remain nonweightbearing.

Obtain an orthopedic consultation for displaced (depressed) fractures, which require open reduction and internal fixation.[18] Articular depression of greater than 3 mm may be considered for surgery.

The goal of treatment is a stable, aligned, mobile, and painless knee joint to minimize risk of posttraumatic osteoarthritis.[19]


Orthopedic referral is recommended for all knee fractures. Nondisplaced fractures may be splinted, with orthopedic follow-up care within a few days. Displaced or open fractures require prompt orthopedic consultation.



Medication Summary

Opioid analgesics and nonsteroidal anti-inflammatory agents are the DOCs for pain associated with fractures.

Nonsteroidal anti-inflammatory drugs (NSAIDs)

Class Summary

Most commonly used for relief of mild to moderate pain. Effects of NSAIDs in the treatment of pain tend to be patient specific, yet ibuprofen usually is the DOC for initial therapy. Other options include flurbiprofen, ketoprofen, and naproxen.

Ibuprofen (Ibuprin, Advil, Motrin)

Usually DOC for treatment of mild to moderate pain, if no contraindications exist; inhibits inflammatory reactions and pain, probably by decreasing cyclooxygenase activity, which results in prostaglandin synthesis.

Naproxen (Anaprox, Naprelan, Naprosyn)

Used for relief of mild to moderate pain; inhibits inflammatory reactions and pain by decreasing cyclooxygenase activity, which decreases prostaglandin synthesis.

Ketoprofen (Oruvail, Orudis, Actron)

Used for relief of mild to moderate pain and inflammation.

Administer small dosages initially to smaller patients, older persons, and those with renal or liver disease. Doses >75 mg do not increase its therapeutic effects. Administer high doses with caution and closely observe patient for response.


Class Summary

Pain control is essential to quality patient care. It ensures patient comfort, promotes pulmonary toilet, and aids physical therapy regimens. Many analgesics have sedating properties that benefit patients who have sustained fractures.

Acetaminophen (Tylenol, Panadol, Aspirin Free Anacin)

DOC for treatment of pain in patients with documented hypersensitivity to aspirin or NSAIDs and in those with upper GI disease or those taking oral anticoagulants.

Acetaminophen and codeine (Tylenol #3)

Drug combination indicated for treatment of mild to moderate pain.

Hydrocodone bitartrate and acetaminophen (Vicodin ES)

Drug combination indicated for the relief of moderate to severe pain.

Oxycodone and acetaminophen (Percocet)

Drug combination indicated for relief of moderate to severe pain; DOC for aspirin-sensitive patients.

Oxycodone and aspirin (Percodan)

Drug combination indicated for relief of moderate to severe pain.

Morphine Sulfate (Duramorph, Astramorph, MS Contin)

DOC for narcotic analgesia due to its reliable and predictable effects, safety, and ease of reversibility with naloxone; IV doses vary and commonly are titrated until desired effect is obtained.




Transfer is appropriate if inpatient beds or operating rooms are unavailable or if an orthopedic specialist's services are indicated.


Complications include the following:

  • Neurovascular injury: This includes popliteal artery injury due to displaced distal femur or tibial plateau fractures and peroneal nerve injury due to proximal fibula fractures.

  • Compartment syndrome of the lower leg: Signs of compartment syndrome include pain with passive movement of the involved muscles, paresthesias, pallor, and a very late finding of pulselessness.[20] Compartment syndrome by definition has increased compartment pressures; therefore, palpation of the affected area frequently aids in the diagnosis.[20] However, a soft extremity does not rule out compartment syndrome. If compartment syndrome is suspected, obtain an emergent orthopedic consultation and measure the compartment pressures. If untreated, increased compartment syndrome can cause permanent disability.[20]

  • Soft-tissue infection

  • Osteomyelitis secondary to an open fracture

  • Delayed union or nonunion

  • Fat embolism

  • Thrombophlebitis

  • Posttraumatic arthritis or knee stiffness

  • Chondromalacia patella

Nonunion, infection, posttraumatic arthritis, arthrofibrosis, symptomatic hardware, and extensor mechanism insufficiency have all been described following patellar repair, and the risk of their occurrence may be augmented by patient-, injury-, and treatment-related factors.[21]

In pediatric patients, complications of healing after tibial fractures are uncommon, although some tibial shaft fractures exhibit delayed union or nonunion, infection, and soft-tissue complications.[22]

Tibial tubercle fractures represent high-energy injuries with potential complications such as compartment syndrome and/or vascular compromise.[23]


A good prognosis is expected with patellar and tibial spine or tubercle fractures.

A fair prognosis is expected with tibial plateau and femoral condyle fractures. A recent prospective study in patients with tibial plateau fractures showed that only 14% of patients recover full quadriceps muscle strength 1 year after injury.[24] Also, 20% will have residual knee stiffness after 1 year.

Patient Education

For excellent patient education resources, visit eMedicineHealth's First Aid and Injuries Center. Also, see eMedicineHealth's patient education articles Knee Dislocation and Knee Injury.[25]