If you are ok with calling .net framework objects you have access to all the methods provided by PerformanceCounterCategory.
The following should help you get started:
$categoryName = "Processor"
$categoryInstance = "_Total"
$counterName = "% Processor Time"
# Call the static method to get the Help for the category
$categoryHelp = [System.Diagnostics.PerformanceCounterCategory]::GetCategories() | ?{$_.CategoryName -like $categoryName} | select -expandproperty CategoryHelp
# Create an instance so that GetCounters() can be called
$pcc = new-object System.Diagnostics.PerformanceCounterCategory($categoryName)
$counterHelp = $pcc.GetCounters($categoryInstance) | ?{$_.CounterName -like $counterName} | select -expandproperty CounterHelp
$categoryHelp
$counterHelp