Psoriatic arthritis is a type of inflammatory arthritis that affects some people with psoriasis. Psoriasis is a condition that causes red, scaly patches to form on the skin.

It affects roughly 30 percent of people with psoriasis, and it’s most common in people between the ages of 30 and 50. There’s no connection between the severity of your psoriasis and the severity of your psoriatic arthritis.

Psoriatic arthritis typically develops after the onset of psoriasis, but some people develop joint pain before they notice any skin-related symptoms.

Here are 11 symptoms to watch for if you think you might have psoriatic arthritis.

Psoriatic arthritis causes inflammation in the joints, which can cause pain, tenderness, and stiffness. You might feel this in just one joint or in several.

Psoriatic arthritis usually affects the knees, fingers, toes, ankles, and lower back. Symptoms of pain and stiffness may disappear at times, and then return and worsen at other times. When symptoms subside for a time, it’s known as a remission. When they worsen, it’s called a flare-up.

Swelling in the joints due to inflammation is a common signs of psoriatic arthritis. Inflamed tissue produces heat, so your joints may also feel warm to the touch.

Changes to your nails, such as pitting, may be an early sign of psoriatic arthritis. Pitted nails appear bumpy or dented. Psoriasis itself can also affect the nails, making them look like they have a fungal infection.

According to the Mayo Clinic, people with psoriatic changes in their nails are at increased risk of developing psoriatic arthritis.

Nails that fall off or separate from your nail bed, called onycholysis, may also be a sign of psoriatic arthritis. This can happen with or without pitting.

Psoriatic arthritis can lead to a condition called spondylitis, which causes swelling in the joints of your spine. In some cases, the sacroiliac joints (SI joints) of the pelvis actually fuse together.

Psoriatic arthritis may begin in smaller joints, such as the those of the fingers or toes, and progress from there. Swollen, sausage-like fingers and toes, called dactylitis, are a hallmark of psoriatic arthritis.

Unlike other types of arthritis, psoriatic arthritis tends to make your entire finger or toe appear swollen, rather than just the joint.

People with psoriatic arthritis may experience eye problems, such as inflammation and redness. If your eyes are inflamed, you may notice irritation, pain, or redness in and around the eye. You may also notice changes in your vision.

Pain in the feet or ankles may be an indication of psoriatic arthritis. People with psoriatic arthritis often develop enthesitis, which is pain in the places where tendons attach to bones. This tends to appear as pain, swelling, and tenderness in your heel (Achilles tendon) or the bottom of your foot.

Enthesitis can also involve the elbow, causing something similar to tennis elbow. Symptoms of enthesitis affecting the elbow include pain, tenderness, and trouble moving your elbow.

One possible sign of psoriatic arthritis is a reduced range of motion in your joints. You might find it harder to extend your arms, bend your knees, or fold forward. You may also have problems using your fingers effectively. This can lead to problems for people who work with their hands in any way, including typing and drawing.

A general feeling of fatigue, ranging from tiredness to exhaustion, is a common symptom in people with psoriatic arthritis. You may begin to have difficulty making it through the day without taking a nap.

Not everyone with psoriasis develops psoriatic arthritis, but it’s important to be aware of its symptoms if you have psoriasis. Treating psoriatic arthritis early can help you avoid further joint damage, so make sure to bring up any new or unusual symptoms to your doctor.