There are a wide range of differentials that can cause the acutely painful limb, ranging from radiculopathies to acute limb ischaemia. And knowing how to approach this presentation is essential, as a missed diagnosis can be potentially limb-threatening.
Lower limb ulcers also can be caused by a wide range of differentials. Whilst there are rare causes, in developed countries they are commonly caused by either arterial disease, venous disease, or from neuropathic causes. Knowing the differentiating factors between them is a commonly asked examination question too!