Working Diagnosis:
Proximal patellar tendon avulsion
Subcortical fracture of the lateral femoral condyle

Treatment:
The patient underwent surgical repair with fiberwire suture via modified Krackow technique.

Outcome:
At 5 weeks post-op the patient had a passive range of motion of 0-30 degrees and was able to perform active straight leg raise. At 7 weeks extension had improved to 90 degrees, and by 9 weeks to 120 degrees. At 12 weeks the patient was ambulating without assistance and was able to extend to 130 degrees. At 19 weeks post-op the patient had a slight extension lag, which resolved with aggressive physical therapy. At 25 weeks post-op he was cleared to advance activity as tolerated. He was expected to make a full recovery.

Author's Comments:
This is a case of a rare complete avulsion of the proximal patellar tendon off the distal patella. Patellar tendon avulsions present most commonly in patients under 40 years of age as a result of a forced hyperflexion injury. Although unable to palpate an infrapatellar gap, other hallmark signs of this injury were present in this case, including acute onset of pain and swelling, loss of active knee extension, and x-ray evidence of patella alta. The patient did not exhibit any historical risk factors for tendon rupture, such as osteochondral disorders, systemic steroid use, or recent fluouroquinolone use.

Editor's Comments:
Proximal patellar tendon avulsion is an uncommon, potentially devastating injury. A high-riding patella is the hallmark diagnostic sign for this injury. Early diagnosis and surgical intervention is necessary. Treatment consists of open reduction and internal fixation.

References:
Ali Yousef MA, Rosenfeld S. Acute traumatic rupture of the patellar tendon in pediatric population: Case series and review of the literature. Injury. 2017 Nov;48(11):2515-2521.

Capogna B, Strauss E, Konda S, Dayan A, Alaia M. Distal patellar tendon avulsion in association with high-energy knee trauma: A case series and review of the literature. Knee. 2017 Mar;24(2):468-476.

Lanzi JT Jr, Felix J, Tucker CJ, Cameron KL, Rogers J, Owens BD, Svoboda SJ. Comparison of the Suture Anchor and Transosseous Techniques for Patellar Tendon Repair: A Biomechanical Study. Am J Sports Med. 2016 Aug;44(8):2076-80.

O'Malley M, Reardon P, Pareek A, Krych A, Levy BA, Stuart MJ. ExtensorMechanism Disruption in Knee Dislocation. J Knee Surg. 2016 May;29(4):293-9.

Saragaglia D, Pison A, Rubens-Duval B. Acute and old ruptures of the extensor apparatus of the knee in adults (excluding knee replacement). Orthop Traumatol Surg Res. 2013 Feb;99(1 Suppl):S67-76.

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