Crossing sign (knee)
The crossing sign is seen on true lateral plain radiographs of the knee when the line of the trochlear groove crosses the anterior border of one of the condyle trochlea. It is a predictor of trochlear dysplasia. Trochlear dysplasia has been linked to recurrent patellar dislocation1,2,4. The crossing sign is sensitive but not specific in diagnosing trochlear dysplasia; sensitivity of 94% and specificity of 56% 3,4.
- 1. Dejour H, Walch G, Neyret P et-al. [Dysplasia of the femoral trochlea]. Rev Chir Orthop Reparatrice Appar Mot. 1990;76 (1): 45-54. - Pubmed citation
- 2. Bollier M, Fulkerson JP. The role of trochlear dysplasia in patellofemoral instability. J Am Acad Orthop Surg. 2011;19 (1): 8-16. J Am Acad Orthop Surg (full text) - Pubmed citation
- 3. O W Donaldson, J Heal, J Mulford, C J Wakeley and J D J Eldridge. Does the plain radiograph accurately predict trochlear dysplasia. J Bone Joint Surg Br 2012 vol. 94-B no. SUPP IX 61.
- 4. Rémy F, Chantelot C, Fontaine C, Demondion X, Migaud H, Gougeon F. [Inter- and intraobserver reproducibility in radiographic diagnosis and classification of femoral trochlear dysplasia]. Surg Radiol Anat. 1998;20(4):285-9. - Pubmed citation