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A 16 year old football player is brought in with severe right knee pain after being hit from the front. He states that he thought his knee was displaced initially, but now it looks back in place. He has no obvious deformity or effusion on observation, and no ecchymosis. Instability testing is difficult due to the patient’s pain. Radiographs are negative for fracture or dislocation. Dorsalis pedis pulses are palpable and normal bilaterally.

In this patient, which of the following is insufficient for assessing for vascular injury?