http://example.com/Controller/Action?param=test

<input data-bind="value: field, <?>"></input> <!-- Either set value to "test" here -->

this.field = ko.observable(<?>) <!-- or here -->

<input type="hidden" id="temp" value="@Model.Param"></input>

field($("#temp").val());

<script type="text/javascript" src="pageViewModel.js"></script>
<script type="text/javascript">
    pageViewModel.setValue(@Model.Param); // Dangerous
</script>