Ankle pain has dozens of possible causes, ranging from a simple twist on an uneven sidewalk to arthritis, nerve problems, and even issues originating in your lower back. The ankle is a complex joint where three bones meet, held together by multiple ligaments and powered by tendons that run from your calf muscles down to your foot. That complexity means many different structures can become a source of pain. Here’s a breakdown of the most common causes and how to tell them apart.
Sprains and Fractures
The most common cause of sudden ankle pain is a sprain. This happens when the foot twists under the leg, stretching or tearing a ligament. Most sprains are “inversion injuries,” where the sole of your foot rolls inward. A mild sprain typically heals in one to two weeks, but a complete ligament tear can take several months to fully recover.
Fractures happen through a different mechanism. They’re more common with rotational force (twisting your body while your foot stays planted) or direct impact, like someone landing on your ankle during a sport. From the outside, sprains and fractures can look nearly identical: both cause swelling, bruising, and difficulty walking. Bruising that pools down into your toes or heel is caused by gravity pulling blood from broken vessels, and it happens with both injuries, so it doesn’t reliably tell you whether a bone is broken.
A few signs suggest you should get imaging rather than waiting it out: tenderness directly over the bony bumps on either side of your ankle, pain where the ankle bends, or an inability to bear weight right after the injury and walk at least four steps. Emergency departments use a version of these criteria (called the Ottawa Ankle Rules) to decide who needs an X-ray, and the rules catch roughly 95% of fractures.
Tendon Problems
Tendons connect muscle to bone, and several major tendons cross the ankle joint. When they become inflamed or start to break down, the pain usually builds gradually rather than striking all at once.
The Achilles tendon, running along the back of your ankle, is the most commonly injured. Achilles tendinitis causes stiffness and pain at the back of the heel, especially first thing in the morning or after sitting for a long time. It’s often triggered by a sudden increase in activity, like ramping up running mileage too quickly, or by footwear that doesn’t support your heel well.
The posterior tibial tendon runs along the inner ankle and supports your arch. When this tendon becomes inflamed or weakened, it causes pain on the inside of the ankle, and over time can lead to a flattening of the arch. In early stages, you can still raise your heel off the ground, though it may hurt. Left untreated, the tendon can stretch out permanently, changing your foot’s alignment and making the problem much harder to correct.
Arthritis
Ankle arthritis falls into two main categories, and they feel different because they work differently.
Osteoarthritis is a wear-and-tear process where the cartilage cushioning the joint gradually breaks down. In the ankle, it most often follows a previous injury, like a bad fracture or repeated sprains that left the joint less stable. The pain tends to be worst during or after activity and improves with rest. Stiffness is common in the morning but usually loosens up within 15 to 30 minutes.
Rheumatoid arthritis is an autoimmune condition where the immune system attacks the lining of the joints. It typically affects both ankles symmetrically and causes more prolonged morning stiffness, often lasting an hour or more. You may also notice warmth, redness, and swelling that doesn’t seem connected to any particular activity. Rheumatoid arthritis can appear at any age, while osteoarthritis is more common after 50 or after joint trauma.
Gout
Gout causes sudden, intense pain that often strikes in the middle of the night. It happens when uric acid in your blood crystallizes inside a joint. The big toe is the most famous target, but the ankle is another commonly affected joint. During a gout flare, the ankle may become so swollen, red, and tender that even the weight of a bedsheet feels unbearable. Flares typically peak within 12 to 24 hours and can last days to weeks. Over time, repeated flares can leave deposits called tophi around the joint, including along the Achilles tendon at the back of the ankle.
Nerve Compression
Tarsal tunnel syndrome is essentially the ankle’s version of carpal tunnel syndrome. A nerve that runs through a narrow channel on the inside of your ankle becomes compressed, causing burning pain, tingling, or numbness along the inner ankle and the bottom of your foot. The symptoms often worsen with standing or walking and may improve with rest. Your doctor can sometimes reproduce the pain by tapping on the nerve at the inside of your ankle.
Not all nerve-related ankle pain starts at the ankle. A pinched nerve in your lower back, particularly in the lumbar spine, can send pain, tingling, or numbness radiating down your leg and into your ankle and foot. This is a form of radiculopathy, and sciatica is the most well-known example. If your ankle pain comes with back pain, leg weakness, or a sensation of pins and needles running down from your hip, the source of the problem may be your spine rather than your ankle itself.
Biomechanical Causes
Sometimes ankle pain isn’t caused by a single injury or disease but by the way your foot moves. Overpronation, where your foot rolls inward too much with each step, gradually flattens the arch and puts extra strain on the muscles, tendons, and ligaments that support the ankle. Over weeks or months of walking or running, that accumulated stress can lead to Achilles tendinitis, posterior tibial tendon problems, or generalized ankle soreness. Flat feet, worn-out shoes, and sudden increases in activity are common contributors. Supportive footwear or custom insoles can often reduce the strain enough to resolve the pain.
Joint Infection
Septic arthritis, an infection inside the joint itself, is less common but serious. It typically causes rapid-onset pain, significant swelling, warmth, redness, and sometimes fever. The ankle becomes extremely painful to move, and symptoms worsen quickly over hours to days rather than weeks. Bacteria usually reach the joint through the bloodstream, though they can also enter through a wound, surgery, or injection. Septic arthritis requires prompt treatment because infection can damage cartilage rapidly. If your ankle becomes acutely swollen and hot, especially if you also feel feverish or generally unwell, that combination warrants urgent evaluation.
Other Common Contributors
Several additional conditions round out the list of frequent ankle pain causes:
- Stress fractures: Tiny cracks in the ankle bones caused by repetitive impact, common in runners and military recruits. The pain is usually mild at first, worsening with activity over days to weeks, and may not show up on a standard X-ray until healing has already begun.
- Bursitis: Inflammation of the small fluid-filled sacs that cushion the joint. In the ankle, this often occurs near the Achilles tendon and can be triggered by tight shoes or repetitive motion.
- Peroneal tendon injuries: The peroneal tendons run along the outer ankle. They can become inflamed, tear, or slip out of position, causing pain on the outside of the ankle that worsens with activity.
- Ankle instability: After repeated sprains, the ligaments may remain stretched and loose, leaving the ankle feeling wobbly and prone to giving way. This chronic instability itself becomes a source of ongoing pain.
Because so many structures occupy such a small area, pinpointing the cause of ankle pain often comes down to the details: exactly where it hurts, how it started, what makes it worse, and whether it came on suddenly or built up over time. Pain on the inner ankle points toward the posterior tibial tendon or tarsal tunnel syndrome. Pain on the outer ankle after a twist suggests a sprain or peroneal tendon injury. Pain that arrives overnight with dramatic swelling raises the possibility of gout or infection. And pain that seems to travel down from your back or hip may have nothing to do with the ankle at all.