How can I make a Player's arm collidable?

This seems simple but I cant find an answer for this. Am trying to make a ragdoll script where the player is still alive. So I've made the script copy the limbs of the character and attached them to the torso with a socket constraint. unfortunately the arms hang through the ground. How do I make the arms collide with the ground?(setting the arms to CanCollide dos not work)

Heres the code I have for the ragdoll script if you are interested...

local character = script.Parent
local player = game.Players:GetPlayerFromCharacter(character)

player.PlayerGui.Health.Changed:connect(function()
    print("HURT")
    if player.PlayerGui.Health.Value > 0 then
        character.Humanoid.PlatformStand = false
    end
    if player.PlayerGui.Health.Value <= 0 then
        character.Humanoid.PlatformStand = true
        local FakeArm = game.Lighting.FakeArm:Clone()
        --find Left Arm
        local children = character:GetChildren()
        for i=1,#children do
            if children[i].Name == "Left Arm" then
                local clone = children[i]:Clone()
                FakeArm.RealArmAttachment.Parent = children[i]
                FakeArm.FakeArmAttachment.Parent = clone
                FakeArm.BallSocketConstraint.Parent = clone
                clone.BallSocketConstraint.Attachment1 = children[i].RealArmAttachment
                clone.BallSocketConstraint.Attachment0 = clone.FakeArmAttachment
                children[i].Transparency = 1
                clone.Parent = character
            end
        end
        FakeArm.Parent = character
    end
end)