Can enthesopathy (on bone scan) at the achilles' tendon insertion; indicate both an old allusion injury and "new" rejury in the same spot.

Depends on phase: Usually enthesiopathy on bone scan is detected when some calcification is in tendon or reactive change in bone where tendon attaches. These findings are usually chronic in nature. If a three phase scan is performed evidence of hyperemia, some increased activity, can be seen on early soft tissue phases(usually acute or subacute injury) which will disappear on delayed osseous phase.

Yes and no: Bone scintigraphy is a very sensitive way to detect this type of enthesopathy. However, the lesion can be seen for several months and sometimes many years after the initial inflammation. It depends on several factors such as repeated trauma or overuse of the lower limbs. The intensity of radiotracer uptake may also vary. If it is mild, it is likely to be an "old" injury. Good luck.