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Figure 1: Frontal View of Normal Patellar Tendon and Extensor Mechanism.

The extensor mechanism consists of the tibial tubercle, the patellar tendon, the patella, the quadriceps tendon, and the quadriceps muscle. The quadriceps muscle (large muscle on the front of the thigh) attaches to the quadriceps tendon which attaches to the patella (kneecap). At the botom of the patella is the patellar tendon. It runs from the inferior pole of the patella (bottom) to the tibial tubercle (front of the tibia or shin bone) just below the front of the knee. As the quadriceps muscle contracts (shortens), it pulls on the quadriceps tendon, the patella, the patellar tendon, the tibia tubercle, and the tibia to move the knee from a flexed (bent) position to an extended (straight) position. Conversely, when the quadriceps muscle relaxes, it lengthens. This allows the knee to move from a position of extension (straight) to a position of flexion (bent). (Click HERE for a computer animation of basic knee motion (mpg file) courtesy of Rob Kroeger.)


When the tibial tubercle is fractured, the patellar tendon loses its attachment to the tibia (shin bone). Without this anchoring effect of the intact patella tendon attachment, the patient is unable to straighten the knee. When a fracture of the tibial tubercle occurs, the knee will usually buckle and give way because the body is no longer able to hold the knee in a position of extension (straight).

Tibial tubercle fractures usually occur in adolescents and typically occur at the growth plate of the proximal (upper) tibia. Unfortunately, the growth plate is structurally weaker then the rest of the bone. For that reason, the abnormal force that causes a patellar tendon rupture in an adult, often results in a tibial tubercle fracture in an adolescent.


The diagnosis is arrived at by talking to the patient and taking a history of how the injury occurred. Usually, patients report that while running or jumping, they felt a pop or crack at the front of the bone below the knee. This is followed by the onset of pain, and the inability to stand or walk. Swelling and bruising rapidly develop. The injury usually causes the patient to go to a hospital for further evaluation. When the physician examines the knee, the examination is usually fairly limited due to the amount of pain that the patient is having. The examination consists of palpating the patellar tendon and the tibial tubercle to identify the area of most intense discomfort and to try to distinguish between a tibial tubercle fracture and a patellar tendon rupture. (Usually, when the tendon ruptures, the patella moves upwards on the thigh. At the same time, the hole between the ends of the ruptured tendon is palpable on the front of the knee.) Due to the pain, it is usually not possible to manipulate the knee to test for ligament or cartilage injury. Fortunately, with a tibial tubercle fracture, the ligaments and meniscal cartilages are rarely injured. Finally, x-rays are taken of the knee. These show the abnormal position of the tibial tubercle, indicating a fracture of this bone.

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Figure 1: Lateral x-ray of knee with tibial tubercle fracture (red circle).

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Figure 2: Lateral x-ray of normal knee with uninjured tibial tubercle (red circle).


The principles of treatment of this injury are those governing the care of fractures. if the fragment is not displaced from its normal position, then a cast may be all that is required for satisfactory healing.

However, if the tibial tubercle fracture has resulted in displacement of the fracture fragment from its normal position, then the normal position must be re-established to allow the patient to have the best opportunity for normal function. Unfortunately, this requires surgery.

At the time of the surgical repair (open reduction and internal fixation or ORIF), an incision is made over the front of the knee at the level of the fracture.

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Figure 3: Frontal view of surgical knee with tibial tubercle fracture.

The patellar tendon is identified as well as the fracture fragments. The injury site is cleaned of debris and hematoma. In figure 2, the tubercle fracture has been elevated to expose the unerlaying fracture site.

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Figure 4: Tubercle fragments are turned upwards to identify the fracture site.

The fracture fragments are then restored to their normal position. This requires manipulating the fragments so that they fit together normally. (The process is similar to taking the pieces of a puzzle and assembling the pieces so that the proper fit is achieved.) Once the proper position has been determined, screw(s) are usually inserted to hold the fragments in place.

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Figure 5: Frontal view with screw reattachment of tubercle fragment.

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Figure 6: Lateral x-ray after open reduction and internal fixation (insertion of screw) at tubercle fracture site.

Following closure of the skin, some type of protective device is applied to the leg. This may be a cast, a knee immobilizer, or a range of motion brace. The goal following surgery is to allow for healing of the injury and rehabilitation of the knee. Typically, as the healing progresses, the stress on the injury site may be increased by increasing the range of motion of the knee and increasing the amount of exercising that a patient is doing. Physical therapy plays an important role in the successful recovery of the knee. Often times, a patient goes to supervised PT several times a week for 4-6 weeks. Recovery is not considered to be complete until the motion has returned to normal and the strength has returned.


The usual risks of surgery are involved including: infection, stiffness, suture reaction, failure of satisfactory healing, risks of anesthesia, phlebitis, pulmonary embolus (blood clot in the lungs), and persistent pain or weakness after the injury and repair. In addition, because of the injury to the growth plate, there is a risk of growth plate injury. Unfortunately, if the plate is damaged, it occurs at the time of the injury. There is no way to reliably predict whether or not a patient will have problems with the growth plate following injury. (For more details, see "Growth plate injuries").

For a REALAUDIO/VIDEO presentation of a tibial tubercle fracture: TIBIAL TUBERCLE FRACTURE

Questions, Comments or Tips on Fractures/Knee Injuries: Post Them at: Orthopedic & Arthroscopic Message Board




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