A 24-Year-Old Man

and Iain McNamara1

Trauma & Orthopaedics, Norfolk & Norwich University Hospital, Norwich, United Kingdom


A 24-year-old painter and decorator complained of problems with his right knee. He first had problems at aged 18 years old when he had a direct blow on the outside of the knee. He said that at this point the kneecap dislocated and came out of joint. He had to pop it back in himself. Since then he had had multiple episodes of dislocation. The knee felt very unstable; it often gave way whilst he was walking. He had been unable to rehabilitate despite efforts in the gym.

Family History

His brother had recurrent patellar instability.


His Beighton score was 7 out of 9. His overall lower limb alignment was normal. He had no effusion in his right knee. The VMO was present but weak. He had marked patellar apprehension ++. His mediolateral glide was at least ++++ with no firm end point. Clinically he suggested that he had a flat trochlea. His patellae tracked with a slight J-shape. He had no end point to his MPFL on the right knee. The knee flexed from −10° to 135°. There was no tibiofemoral joint line tenderness. He was Lachman’s ++, Anterior drawer ++, jerk test +, and MCL−.



Question 1

What do the plain radiographs show?


MRI Report

A well-corticated bony fragment adjacent to the medial aspect of the patella, the bony fragment, measures 12 × 6 mm in size. This is located at the insertion of the medial patellar ligament/retinaculum. There is no associated bone oedema to suggest a recent injury. There is satisfactory articular cartilage of the patella and the adjacent trochlear groove. There is a relatively shallow trochlear groove [The boss height measures 3 mm]. The medial patellar retinaculum or ligament does not appear attenuated.

There is a complete tear of the anterior cruciate ligament. The posterior cruciate ligament is intact. Intact menisci with no features to suggest meniscal tears. The articular surfaces of the medial and lateral tibiofemoral compartments are intact. There is evidence of a previous injury of the medial collateral ligament which is thickened. Satisfactory appearances of the fibular collateral ligament. No significant joint effusion or synovitis.


No features to suggest a recent patellar dislocation. The well-corticated bony fragment on the medial border of the patella suggests a previous patellar dislocation with a small avulsed fragment at the insertion of the medial patellar retinaculum.

The anterior cruciate ligament is torn.

Question 2

What is the bony fragment at the proximal part of the medial femoral condyle?

Question 3

What is the diagnosis of this man’s right knee problem?

Sep 26, 2017 | Posted by in ORTHOPEDIC | Comments Off on A 24-Year-Old Man

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