The trochlear groove is the concave surface where the patella (kneecap) makes contact with the femur (thighbone). Also called the 'trochlea'.

trochlear groove

As the knee bends, the patella engages with the groove and is contained by its steep walls.

patella in trochlear groove

Towards the top of the trochlear groove the walls are flatter. When the knee is in extension (straight) and the patella in the upper part of the groove, it is more easily able to disengage (sublux).


An abnormal trochlear groove

Sometimes the groove is abnormal - trochlear dysplasia - and this may result in patellar instability.


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

Knee bones from above

Simple illustrations to give a birds' eye view of the knee bones.

Knee bones from side

Bony anatomy of the knee, in simple terminology.

Patellar instability and dislocation

Discussing how the anatomy can affect the tendency to dislocate the patella.



The sulcus line of the trochlear groove is more accurate than Whiteside’s Line in determining femoral component rotation. Talbot S, Dimitriou P, Radic R, Zordan R and Bartlett J. Knee Surg Sports Traumatol Arthrosc. 2015; 23(11): 3306–3316.

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