Trochear dysplasia is a condition where the  trochlear groove is abnormal, usually at its upper end, at which point the groove is abnormally flat or even heaped into a 'bump'.

mild trochlear dysplasia with shallow trochlea trochlear dysplasia with a flat upper trochlea with no groove trochlear dysplasia with a trochlear bump
Mild trochlear dysplasia with a shallow trochlear groove. More severe situation where the upper trochlea has no groove at all. Instead of being convex, the trochlear at its upper end forms a concave 'bump', and the patella finds no comfortable groove into which to engage.


Trochlear dysplasia and kneecap instability

Trochlear dysplasia is commonly associated with an unstable patella (kneecap), and patellar dislocation.

dysplastic trochlea
trochlear bump

The unstable patella

A discussion about patellar instability, the factors that may cause the patella to sublux or dislocate, and what can be done about it.

Illustrated article showing how the patella starts its engagement with the groove of the trochlea.

Video demonstrating the J sign

This is the Editor's interpretation of a paper published in the orthopaedic literature in 2016.

Explaining how the kneecap glides within the underlying groove of the femur bone.

This video is a record of a meeting held by Dr Lars Blønd in order to bring together his patients who have all had the procedure of arthroscopic trochleoplasty.




Trochlear dysplasia and patella tilt


The effect of trochlear dysplasia on patellofemoral biomechanics: a cadaveric study with simulated trochlear deformities. Van Haver A, De Roo K, De Beule M, Labey L, De Baets P, Dejour D, Claessens T, Verdonk P. Am J Sports Med. 2015 Jun;43(6):1354-61.

See also -

eBook on patellar instability

Factors contributing to an Unstable Patella - ebook

VIDEO putting trochlear dysplasia into context