Which combination of findings MOST urgently requires emergency referral in a patient with low back pain?

• 1 Morning stiffness in the back that eases within 20 minutes
• 2 Pain that is reproduced by palpation over the lumbar paraspinal muscles alone
• 3 New urinary retention with saddle numbness and bilateral leg weakness ✓ 정답
• 4 Unilateral calf pain that increases at the end of a long walk

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