The inter-tester reliability of a clinical measurement used to determine the medial/lateral orientation of the patella

An important aspect of the patellar taping technique, a common treatment for patellofemoral pain is the assessment of patellar position. The inter-tester reliability of the assessment method has been regarded as poor, as has the validity (Powers et al. 1999). The purpose of the study was to determine inter-tester reliability of a group of trained manual physiotherapists. This was achieved using a clinical measurement to assess the medial/lateral orientation of the patella and compare these findings against a known criterion valid measurement of patella position. Twenty experienced manual physiotherapists evaluated medial/lateral orientation of the patella. The findings of the clinical assessment were then compared to the position of the patella as determined through magnetic resonance imaging (MRI). The MRI and the clinical assessment were carried out on the right knee of a single subject, who was supine with the knee in 20 degree flexion with the quadriceps relaxed. Both measures found the patella to be laterally displaced. Using the clinical method the mean difference between medial and lateral measurements was 6.4 mm (+/- 3.9 mm). The MRI measure of lateral patella displacement found the patella to be displaced 5 mm laterally. The inter-tester reliability of the clinical test showed good agreement, r = 0.91 for the medial measure and r = 0.94 for the lateral measure. The agreement between the clinical and MRI measures was (r = 0.9) which was also a significant agreement. This study appears to demonstrate that experienced manual physiotherapists can reliably measure relative patella medial/lateral position