Easily Missed Injuries Around The Knee

Easily Missed Injuries around the Knee Radiographics 1994; 14: 1191-1210 R 劉志 強

Introduction • Injuries to proximal tibia – Tibial plateau fx, Segond fx, Tibial spine fx, Cancellous stress fx

• Injuries to fibular head and tibiofibular joint – Tibiofibular joint dislocation, Fibular head fx

• Injuries to patella – Patellar fx, osteochondral injuries

• Injuries to patellar and quadriceps tendon • Injuries to distal femur – Femoral condyle fx, Osteochondral fx,

• Salter-Harris type fx

Tibial Plateau Fx • Minimally depressed tibial plateau fx, defined as those with displacement or depression of less than 4mm

Tibial Plateau Fx • Fx no seen on AP or lat view may sometimes be visualized on tangential or tunnel view • Should be evaluated with CT for determining the extent of articular surface involvement, establishing the location of fracture fragments

Segond Fx • The Segond fx is a small vertical avulsion of the proximal lateral tibia immediately distal to the tibial plateau. • Precipitating injury usu. involves internal rotation associated with varus stress • Fx fragment is usu. Elliptical and 10X3mm in size, and about 3mm displacement from tibial metaphysis

Segond Fx

Segond Fx • Although minor appearing, associated with a high incidence of coexisting ACL and meniscal injuries

Tibial Spine Fx • Result from either torsional forces about the knee or hyperflexion or hyperextension forces causing avulsion of the intercondylar eminence or the attachments of the cruciate ligaments • one of most common knee injuries in children; most common between ages of 8-14 yrs • commonly caused by fall from bicycle or motorcycle

Tibial Spine Fx • Categorized into 4 types

Stress Fx • The proximal tibia is the most common stress fx about the knee • On plain radiographs, a vague band of increased sclerosis or endosteal callus may be visualized

Stress Fx

Initial imaging was unremarkable, MR image 10 days later shows an irregular horizontal band of low signal intensity surrounded by bone marrow edema

Proximal Tibiofibular joint Dislocation • Estimated 60% of all cases are unrecognized at initial presentation • 4 types have been described • Making the correct diagnosis usu. requires clinical suspicion • A well positioned lateral radioraph is the most useful projection

Proximal Tibiofibular joint Dislocation

Mild widening of the interosseous space on the left Lateral film demostrates incongruity of the proximal tibiofibular joint -----> Ant Lat dislocation

Fibular Head Fx • Results from injury producing excessive varus stress about the knee • Peroneal nerve and anterior tibial artery may be injured • Lateral capsular and ligamentous disruption and peroneal nerve – Lateral compartment syndrome of the knee / Ligamentous peroneal nerve syndrome

Patellar Fx • May be classified as stellate or comminuted; longitudinal or marginal; transverse, proximal or distal pole

Patellar Tendon Injury • Clinical presentation is usu. diagnostic • A soft tissue opacity due to hematoma or hemorrhage can be seen in the region of patellar tendon on lateral radiograph • A high riding patella, or patella alta can be seen • Patella position may appear normal with knee in full extension

Patellar Tendon Injury

Quadriceps Tendon Injury • Rupture of the quadriceps tendon tends to occur in older population • The normally sharp fat planes are obscured by hemorrhage and hematoma • A low riding patella, or patella baja may be seen

Quadriceps Tendon Injury

Note How the Patella is Abnormally Tilted and Positioned on the right compared to the left

Femoral Condyle Fx • Usually occur as a result of varus or valgus stress along with axial loading forces • With associated tibial plateau fx • Isolated fx of the femoral condyles are uncommon • Fractures are often Y or T shaped, extending into intercondylar notch and are both intraarticular and intracapsular

Femoral Condyle Fx

Non displaced lateral femoral condyle fracture

Osteochondral fracture • The cartilage covering the end of a bone in a joint (articular cartilage) is torn • The fracture creates bone or cartilage fragments that can range in size and in depth • Frequently found on the weight bearing surfaces of the femur, can also occur under the patella

Osteochondral fracture

Osteochondral fragment in the joint space

Osteochondral fracture • Osteochondral fx of the lateral femoral condyle often accompany tears of the ACL

Salter-Harris Type Fracture

Conclusion