162 - The Relationship Between the Medial Knee Joint Gap and Medial Collateral Width in Individuals Without Knee Injury

Poster Board Number: 162
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Abstract Body : Introduction
An improved understanding of the structures that provide valgus knee stability will provide insight into the mechanisms leading to the development of medial knee injury. The width of the medial joint gap (MJG) measured on radiographs has been used as an objective measure of medial knee stability. But the ratio between the width of the MJG and the medial collateral ligament (MCL) measured on ultrasound images has not been reported. The current study explored the relationship between the width of the medial knee joint gap and the medial collateral ligament (MCL).
Methods
Eighteen volunteer participants without a history of medial knee injury were recruited for the study. The width of the MJG and the MCL were measured on ultrasound images collected on the participants’ right and left knees while the knee was in full extension. Three images were collected of each knee, and the mean MJG and MCL width were entered into statistical analysis. Pair T-tests were used to determine differences between the right and left sides and Pearson correlation analysis was to determine the relationship between participants’ weight and height and the MJG and MCL width.
Results
The mean medial joint gap was 6.4 ± 0.53mm on the right knee and 6.3 ± 0.63mm on the left knee. The width of the right MCL was 2.2 ± 0.19mm and the left MCL width was 2.2 ± 19mm. The was not a statistical difference between the right and left side medial joint gap or the MCL width. The MCL and the MGP width ratio were 0.35 ± 0.04 on the right and 0.35 ± 0.05 on the left side. A low correlation was found between the participants’ weight and the MJG on both the right (r = 0.437, P = 0.70) and left sides (r = 0.440, P = 0.068), and weak correlations were found between the participants’ weight and MCL width. Weak correlations were found between the participant’s height and MJG and MCL width on both the left and right sides.
Conclusion
The ratio between the width of the MCL and the MJG is consistent at 0.35. But there does not appear to be a relationship between the height or weight of the participant and the width of the MJG or MCL. The MCL is the primary constraint to knee valgus. The width of the MCL should be correlated to the loads placed on the ligament. The participants in the current study did not have a history of medial knee injury and did not have a high level of physical activity. A greater ratio might be seen in individuals that place greater valgus loads on their knees while a lower ratio might be seen in individuals with a history of a medial knee injury.
Significance and implications
A thicker MCL should provide greater resistance to knee valgus. Future studies on this line will include patients with a medial knee injury and will test the change in the width of the MJG with an applied valgus load. Individuals with thicker MCL will likely have less increase in the width of MJG during applied valgus stress.