Abstract
A number of validated knee outcome rating scales are used to assess knee function in the ACL-deficient and ACL-reconstructed knee. These scores use a numeric system to rate findings such as pain, swelling, subjective assessment of function and level of activity.
However, it is unknown whether there is a correlation between the outcome rating scales and whether they can be used interchangeably. The aim of this study was to investigate the correlation between the four commonly used outcome rating scales (Lysholm, IKDC, Cincinnati and Tegner).
Inclusion criteria included physically active patients between the age of 18 and 35 years with isolated ACL injuries. A power calculation for sample size was performed. Selecting an alpha level of 0.05 and power value of 0.8, 24 ACL- deficient and 24 ACL-reconstructed subjects were needed to achieve adequate statistical power. Statistical analysis included the calculation of means and standard deviations for the dependant variables. Pearson's product moment correlation coefficients were used to establish the strength of the relationships.
Forty-four ACL-deficient and 24 ACL reconstructed subjects (mean age 27.0, range 16–49), with a minimum of 12 months post surgery, completed the tests. Pre-operatively, strong significant correlations (r=0.53-0.74, p=0.0001-0.001) between IKDC and the other scoring systems (Cinncinati, Lysholm and Tegner) were observed. The Lysholm score was significantly correlated to IKDC (r=0.74, p=0.0001) and Cinncinati (r=0.60, p=0.001) scores. Non-significant moderate correlations were observed between Lysholm and Tegner (r=0.38, p=0.17) and Cinncinati and Tegner (r=0.36, p=0.18) scores. Post-operatively all scores were strongly related (r=0.61- 0.93). However, only the relationships between Lysholm and IKDC score (p=0.001) and IKDC and Cinncinati score (p=0.01) reached statistical significance.
The results of this study indicate that the commonly used rating scales produce interchangeable results in the ACL-deficient patient. In the ACL-reconstructed patient, knee scoring systems seem to measure different aspects of physical activity, physical disability and subjective patient satisfaction—all of which are not interchangeable. As such, the classification of results may vary and may explain the findings.
