What is the diagnosis?

Tibial tubercle fracture

• Pearl: Other injuries that could cause pain and similar exam findings would include patellar tendon rupture. 

What is the mechanism of injury and are certain patients at greater risk?

Tibial tuberosity fractures are caused by concentric quadriceps contraction or eccentric quadriceps contraction. Normally these are low energy injuries and occur with planting the foot and pushing off or after landing from a jump.  

Early adolescent males are at much higher risk of this injury due to multiple pathophysiological reasons: 

• 2 ossification centers 

• Change in cartilage morphology predisposing it to be weaker to shear forces as patient gets closer to skeletal maturity

• Physis closes in posterior to anterior fashion

What physical exam findings are expected?

Patients typically have a knee effusion, tenderness along the proximal tibia, extensor lag or complete disruption of the extensor mechanism. 

Which imaging modalities can be used?

Plain radiographs, including AP and lateral should be obtained of the knee. Internal rotation view can also be obtained as this will bring the tubercle into profile and allow for closer examination of displacement. If there is diagnostic uncertainty, CT imaging can be used as well (Image 2).

Image 2. CT image showing fracture exiting posteriorly. Author’s own image

What is the management in the ED?

These patients should undergo closed reduction that often requires procedural sedation [7]. 

• Pearl: Patients should be positioned in full extension and overlying pressure used to reduce the fracture. Occasionally the extensor retinaculum will be caught in the fracture preventing adequate reduction.

• Pearl: ~4% can develop compartment syndrome and need close neurovascular monitoring. 

Immobilization can be achieved with placement of a long leg splint and made non-weight bearing.

When do you consult Orthopedics?

Type I and Type II injuries with less than 2 mm displacement following reduction can be placed in long leg cast NWB and follow up outpatient with ortho. Orthopedics should be consulted for Type II with inadequate reduction >2 mm, and all type III, IV, and V, open fractures, neurovascular compromise, and irreducible fractures due to interposed soft-tissue blocking reduction as these will likely require surgical intervention. 

What are the outcomes and potential complications?

Overall patients heal well from this injury and 99.4% return to sport. There is low incidence of leg length discrepancy. Patients are at risk for post-operative stiffness, or bursitis (from hardware). In general they are at risk for compartment syndrome, or recurvatum deformity (due to anterior growth arrest).

• Pearl: Always consider vascular injury when dealing with injuries around the knee.