Question

A teenaged girl complains of pain in the knee on climbing stairs and on getting up after sitting for a long time. What is the probable diagnosis?

• A. Chondromalacia patellae
• B. Plica syndrome
• C. Bipartite patella
• D. Patello-femoral osteoarthritis

Hint:

Young female plus the theatre sign equals softening of patellar cartilage.

Answer 1

The Correct Option is A

Approach this question through pattern recognition of anterior knee pain syndromes. The vignette gives three discriminating clues: a young female, pain when climbing stairs, and pain on standing up after a long period of sitting. The latter is the classic theatre sign (also called the movie sign), and together these point to overload of the patellofemoral compartment. The disorder that fits this exact picture in an adolescent female is chondromalacia patellae, in which the hyaline cartilage on the back of the kneecap softens, fissures, and degenerates, commonly because the patella does not track smoothly in the trochlear groove. Activities that drive the patella hard against the femur, such as ascending stairs or extending the knee after prolonged flexion, reproduce the pain and may cause crepitus. Working through the alternatives: plica syndrome is usually post-traumatic or overuse related and lacks this textbook sitting-then-rising pattern; a bipartite patella is an unfused secondary ossification centre that is generally a silent incidental finding; and patellofemoral osteoarthritis is a degenerative condition of older adults, which is inconsistent with a teenager. The age, sex, and the theatre sign converge on one diagnosis. $\text{Adolescent female} + \text{theatre sign} + \text{stair pain} \Rightarrow \text{chondromalacia patellae}$.
\[\boxed{\text{Chondromalacia patellae}}\]