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Your knee aches on the stairs. Your knuckles feel stiff for the first twenty minutes of every morning. Or there’s a deep throb in one hip that appeared out of nowhere and has decided to stay. Joint pain is stubborn that way. It rarely announces its cause, and a very similar ache can come from wildly different problems.
Roughly one in four adults has been diagnosed with arthritis, and that’s only one branch of the story. Sports injuries, crystal deposits, bacterial infections and even an underactive thyroid can all surface as joint pain. What follows are the seven causes doctors see most often, with the specific details that help separate them.
1. Osteoarthritis: The Most Common Cause of Joint Pain
Osteoarthritis is what happens when the cartilage cushioning a joint thins out over years. It shows up most often in the knees, hips, the base of the thumb, the neck and the lower spine. In the UK, knee osteoarthritis alone accounts for a huge share of musculoskeletal GP visits, and it’s the reason stair-climbing becomes a negotiation for many people over 50.
The pattern is fairly predictable. Pain gets worse with use and eases with rest. Morning stiffness clears within about 30 minutes. You may hear grinding or crackling when the joint moves, and the joint can look knobbly, particularly at the finger joints nearest the nails. Doctors used to call this simple wear and tear; the modern view is that low-grade inflammation is involved too, which is why flare-ups happen even when you haven’t done anything unusual.
Don’t assume the spine is immune. Osteoarthritis of the small facet joints in the lower back is one of the most frequent drivers of chronic back pain, and it often gets blamed on discs or muscles instead.
2. Inflammatory Arthritis and Autoimmune Disease
Here the immune system attacks the joint lining rather than the cartilage wearing down. Rheumatoid arthritis is the best known, but psoriatic arthritis, ankylosing spondylitis and lupus-related joint pain all behave in their own ways. Together they make up a group of conditions where getting the right label genuinely changes treatment, which is why clinicians spend so much time distinguishing the different types of arthritis from one another.
Clues that point to inflammation rather than wear
- Morning stiffness lasting an hour or longer, not 15 minutes
- Joints that feel better once you get moving, and worse after rest
- Swelling in the same small joints on both sides of the body
- Fatigue, low-grade fever or generally feeling unwell alongside the pain
- Pain that comes with rashes, dry eyes, mouth ulcers or gut symptoms
Those last clues matter. Autoimmune conditions travel in packs, and joint pain is often the first thing noticed. Recognising the early signs of autoimmune disease can shave months off the diagnostic journey.
3. Injury, Overuse and Old Damage That Never Settled
A torn meniscus, an ACL rupture, a shoulder that was dislocated at 19, a wrist fracture that healed slightly out of line: all of these leave a joint more vulnerable. Research consistently shows that a significant knee injury in your twenties raises the odds of osteoarthritis in that same knee by the time you’re in your forties or fifties. The joint doesn’t forget.
Overuse injuries work differently. They build up gradually from repeated loading rather than a single event, so the pain appears without a memorable moment of damage. A runner whose knee aches after every 10K, a plasterer with a sore shoulder, a new parent with thumb pain from lifting a baby: the pattern of activity tells you as much as the joint itself.
4. Gout and Other Crystal Deposits
Gout happens when uric acid crystallises inside a joint. It’s famous for attacking the base of the big toe, but the midfoot, ankle, knee and even the fingers are fair game. The attack is dramatic: a joint that’s red, hot, swollen and so tender that a bedsheet feels unbearable. Symptoms typically peak within 12 to 24 hours, which is much faster than most other joint problems.
Pseudogout involves a different crystal (calcium pyrophosphate) and tends to hit the knee or wrist of older adults, often with a similar sudden onset. Common gout triggers are worth knowing:
- Beer and spirits, particularly in quantity
- Shellfish, sardines, anchovies and organ meats
- Sugary drinks and fructose-heavy diets
- Water tablets and some blood pressure medications
- Dehydration, fasting and sudden illness
5. Bursitis and Tendinitis Around the Joint
Sometimes the joint itself is fine and the problem sits in the soft tissue right next to it. Bursitis is inflammation of the fluid sacs that reduce friction; tendinitis (more accurately tendinopathy) is damage to the tendon where it attaches. Both produce a pain that’s sharp and pinpoint on one specific spot rather than spread across the whole joint.
Classic examples include the outer hip (trochanteric bursitis), the shoulder’s subacromial space, the outside of the elbow from repetitive gripping, and the Achilles tendon. These are often confused with arthritis because the area is adjacent, but an ultrasound usually sorts it out in minutes. Metabolic problems raise the risk considerably, so it’s worth knowing that endocrine disorders such as hypothyroidism and diabetes are linked to frozen shoulder, carpal tunnel and stubborn tendon problems.
6. Joint Infection
Septic arthritis is the one cause on this list that can destroy a joint in days. Bacteria enter the joint space, usually through the bloodstream, and the result is a single joint that becomes intensely painful, hot and swollen, often with fever and chills. People who’ve had recent joint surgery, an injection, a skin infection, or who have a weakened immune system are at higher risk.
Reactive arthritis is a different animal, kicking in one to four weeks after an infection in the gut or urinary tract. It often brings eye inflammation and a sore heel alongside the joint pain, and it’s a known companion of inflammatory bowel disease. Lyme disease and some viral infections can also leave joints swollen and achy for weeks.
7. Systemic Conditions Where the Joint Isn’t the Real Problem
Not all joint pain starts in the joint. An underactive thyroid can produce widespread aches, muscle cramps and swelling in the hands and feet. Vitamin D deficiency causes bone and joint pain that mimics arthritis closely, especially in winter or in people who cover their skin or work indoors. Some medications, including certain statins, breast cancer drugs in the aromatase inhibitor class, and fluoroquinolone antibiotics, are infamous for joint and tendon pain.
Referred pain is another trap. A hip that has worn out often presents as knee pain, which is why examining the knee alone leads nowhere. Nerve root irritation from the spine can shoot pain down a limb in a way that feels like the joint is the culprit. Depression, poor sleep and chronic stress turn up the volume on pain signalling too, without any structural damage at all.
Red Flags That Need Medical Attention Fast
Most joint pain can wait for a routine appointment. Some can’t. Book the same day, or go to urgent care, if any of the following apply:
- One joint is suddenly hot, red and swollen, especially with a fever
- You genuinely cannot bear weight on the leg or move the limb
- The joint looks deformed or you heard a pop at the time of injury
- Numbness, tingling or weakness runs down the limb alongside the pain
- Pain started after a tick bite, travel, or a course of antibiotics
- Weight loss, night sweats or fevers accompany the joint symptoms
For everything else, the useful thing you can do before your appointment is write down the pattern: which joints, how long the morning stiffness lasts, what makes it better, what makes it worse, and whether anything else in your body has changed lately. That short record narrows seven possible causes down to two or three faster than almost any test, and it gives your doctor a running start.
