[Robert B. Osgood (1873–1956), orthopedic surgeon in Boston, USA]

[Carl Schlatter (1864–1934), surgeon in Zurich, Switzerland]

= chronic avulsion injury of the attachment of the patellar ligament to the tibial tuberosity (= traction osteochondritis, NOT osteonecrosis); bilateral in 25–50%

Age: 10–15 years; M >F

Anatomy: tibial tubercle develops as an anterior extension of proximal tibial physis; closes at 13–15 years (in girls) and 15–19 years (in boys)

Cause: repetitive microtrauma (common in sports that involve jumping, kicking, squatting)

• local pain + tenderness on pressure
• painful visible swelling of overlying soft tissue
• soft-tissue swelling in front of tuberosity ← edema of skin + subcutaneous tissue
• thickening + calcification of distal portion of patellar tendon
• indistinct margin of patellar tendon
• obliteration of inferior angle of infrapatellar fat pad
• separation of several small ossicles from the developing ossification center of tibial tuberosity (= reactive secondary heterotopic bone formation)
• single / multiple ossifications in avulsed fragment
• comparison with other side ( irregular development normal)

MR:

• patellar tendon enlargement
• increased SI at tibial insertion site of patellar tendon on T1WI + T2WI
• distension of deep infrapatellar bursa
• bone marrow edema adjacent to tibial tuberosity + tibial apophysis (rare)
• thickened cartilage anterior to tibial tubercle

Cx: tibial tubercle fracture with nonunion of bone fragments, patellar subluxation, chondromalacia, avulsion of patellar tendon, genu recurvatum

Rx: immobilization / steroid injection

DDx:

1. Normal irregular ossification pattern of tibial tuberosity between ages 8–14 (asymptomatic)
2. Osteitis: tuberculous / syphilitic
3. Soft-tissue sarcoma with calcifications