Ankylosing spondylitis is a type of arthritis that usually causes lower back pain, but it can also affect other joints.
Ankylosing spondylitis (AS) is estimated to affect 0.9% to 1.4% of people in the United States.
People with AS can develop leg pain if their knees or hips are affected. Very rarely, people with AS can develop a condition called cauda equina syndrome, when the nerves branching off the end of the spinal cord are compressed. This syndrome can lead to permanent disability if left untreated.
Read on to learn more about how AS can affect your legs and how to treat symptoms.
AS is a type of arthritis that develops when your immune system attacks healthy cells in your joints.
These attacks lead to inflammation that can cause symptoms like pain and stiffness. The most common place to develop these symptoms is your lower back, but you may also experience symptoms in other joints, such as your:
- upper back
AS and knee pain
Knee pain in people with AS is asymmetrical, meaning that only one knee is affected or that one knee is affected worse than the other.
Studies have reported hip involvement in as many as
Having symptoms for a longer period of time or having a more advanced disease was associated with more severe hip symptoms. A higher body mass index (BMI) was associated with a higher risk of needing hip replacement surgery.
Ankylosing spondylitis and cauda equina syndrome
Cauda equina syndrome is a rare complication of AS. It develops from the compression of nerves at the end of your spinal cord.
In a 2019 study, researchers examined the features of cauda equina syndrome in six people with AS. All six people had AS for decades before cauda equina syndrome appeared.
AS symptoms generally get worse during flare-ups that can last between weeks to months. Symptoms generally improve between flare-ups.
AS and knee and hip pain
Knee or hip pain tends to be worse after periods of inactivity or when you first wake up. It may improve after exercise. The pain will likely come on gradually and affect one side more than the other.
If your knee is involved, you may have:
- tenderness to the touch
- warmth around the joint
According to the authors of a
The Spondylitis Association of America notes that hip involvement may cause pain in other parts of your lower body, such as your knee or the front of your thigh. When this happens, it’s called referred pain.
Ankylosing spondylitis and cauda equina symptoms
Cauda equina syndrome can cause:
Sciatica is an impingement of your sciatic nerve. Your sciatic nerve is the longest nerve in your body. It runs from your lower spine and its branches reach your feet.
Sciatica and AS can both cause lower back or leg pain, and symptoms can be similar. Sciatica is a much more common condition. It’s estimated to affect
Sciatica can cause:
- shooting pain in your lower back, buttocks, and the back of your leg
- pain that gets worse when you move
- numbness, burning, or weakness in your legs or feet
- pins and needles in your toes or feet
- loss of bowel or bladder control
AS doesn’t have a cure, but a combination of lifestyle changes and medications can help you manage symptoms.
Knee and hip pain treatment
You can often manage knee and hip pain caused by AS at home. Your doctor may recommend:
- getting regular low impact exercise
- eating an anti-inflammatory diet
- taking certain medications, such as:
Your doctor may also recommend a total knee replacement or total hip replacement if more conservative options aren’t working. These surgeries involve replacing your joint with an artificial prosthesis.
Cauda equina syndrome treatment
Surgery can treat cauda equina syndrome.
It’s important to get treatment as soon as possible. If it’s not treated quickly, you may experience permanent paralysis or urinary or bowel incontinence.
AS is a progressive condition that can lead to new symptoms over time. It’s a good idea to visit your doctor anytime you develop new symptoms or if your symptoms get worse.
It’s also a good idea to visit a doctor for an evaluation if you suspect you may have AS but haven’t yet received a diagnosis.
AS is an autoimmune condition that usually causes pain and stiffness in your lower back. It may also cause symptoms in other joints. You may have leg pain if your knees or hips are affected.
Cauda equina syndrome is a rare complication of AS. It develops when the nerves at the end of your spinal cord are compressed. It typically needs to be treated with emergency surgery.