This is one of the most common early symptoms. Patients may feel pain and stiffness in the lower back or buttocks. This pain may worsen after prolonged sitting or lying down, and improve with activity. However, as the disease progresses, the pain may gradually worsen and become persistent.
Patients with ankylosing spondylitis may feel stiffness in the lower back when they wake up in the morning, which can be relieved after some activity. The duration and severity of morning stiffness can be an indicator of disease activity.
Some patients may experience alternating buttock pain, where pain on one side subsides and then occurs on the other side. This symptom may indicate involvement of the sacroiliac joints, an early sign of ankylosing spondylitis.
Although primarily affecting axial joints, patients with ankylosing spondylitis may also develop peripheral arthritis, such as pain, swelling, and restricted movement in the knee, ankle, or hip joints. These symptoms may precede axial joint symptoms.
About a quarter of ankylosing spondylitis patients may develop ocular symptoms such as conjunctivitis or iritis. These inflammations can cause red eyes, pain, blurred vision, or sensitivity to light.
Some patients may experience systemic symptoms in the early stages of the disease, such as low-grade fever, fatigue, loss of appetite, and weight loss. These symptoms are usually non-specific but may be related to disease activity.