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J Bone Joint Surg Br. 2008 Jul;90(7):870-3. doi: 10.1302/0301-620X.90B7.20111.

The effect of quadriceps contraction during weight-bearing on four patellar height indices.

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Centre for Arthroscopic and Shoulder Surgery, IASO General Hospital, Athens, Greece.


The effect of weight-bearing on the height of the patellar using four radiological indices was studied in 25 healthy men using lateral radiographs of the knee in 30 degrees of flexion non-weight-bearing and weight-bearing. The position of the patella was quantified using the Insall-Salvati, the modified Insall-Salvati, the Blackburne-Peel and the Caton indices. The contraction of the quadriceps on weight-bearing resulted in statistically significant proximal displacement of the patella with all four indices studied. The mean Insall-Salvati index was 0.919 (SD 0.063) before and 1.109 (SD 0.042) after weight-bearing (p = 0.001), while the mean modified Insall-Salvati index was 0.734 (SD 0.039) before and 0.896 (SD 0.029) after weight-bearing (p = 0.041). Similarly, the Blackburne-Peel index was 0.691 (SD 0.09) before and 0.807 (SD 0.137) after weight-bearing (p = 0.012). The mean Caton index was 0.861 (SD 0.09) before and 0.976 (SD 0.144) after weight-bearing (p = 0.023). The effect of quadriceps contraction should be considered in clinical studies where the patellar position indices are reported.

[Indexed for MEDLINE]

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