Pathology
- Acute traumatic condition representing chondral or osteochondral avulsion injury at the inferior pole of the patella (the proximal attachment of the patellar tendon)
- Usually occurs between the age of 8 to 12 years of age, when patellar ossification is nearly complete
- The mechanism is usually a powerful contraction of the quadriceps muscle applied to a flexed knee
Symptoms
- Pain and swelling around the inferior pole of the patella
- Inability to straight leg raise
- On x-ray (lateral)
- Will likely have “Patella Alta” (high riding patella) where the the distance between the patella and the tibial tubercle is greater than 1.1*patella vertical height (green arrows)
- On a true lateral (not the Horizonal Beam view), with knee slightly flexed, Blumensaat’s line (red line) should point to the inferior pole of the patella
- MRI may be necessary if x-ray is normal (as the injury may only be cartilaginous)
Management
- Treatment is surgical – injury is NOT TO BE MISSED!