Osteoarthritis

What it is

Osteoarthritis is the most common arthritis, affecting about 528 million people worldwide in 2019 and causing joint pain, stiffness, and reduced function. It is often called OA, degenerative joint disease, or “wear-and-tear” arthritis, but that label is incomplete because OA affects the whole joint, not just cartilage. Modern research shows it involves cartilage breakdown, changes in the underlying bone, inflammation of the joint lining, and effects on ligaments and surrounding muscles. The knee is the single most commonly affected joint globally, with WHO estimating about 365 million people living with knee OA.

OA most often affects the knees, hips, hands, and spine. It becomes more common with age, but it is not an inevitable part of ageing. Risk rises with prior joint injury, obesity, repetitive joint loading, some metabolic conditions, and structural joint problems. Women are affected more often than men, especially after midlife.

A simple way to think about OA is that the joint's normal repair processes no longer keep up with mechanical stress and tissue damage. Symptoms usually develop gradually and can range from mild intermittent pain to major disability.

Commonly affected joints	Typical symptoms
Knee	Pain with walking, stairs, stiffness after rest, swelling
Hip	Groin or buttock pain, reduced range of motion, limp
Hand	Bony enlargement, pain, reduced grip, finger stiffness
Spine	Neck or back pain, stiffness, sometimes nerve-related symptoms

How it works

OA is now understood as a disease of the entire joint as an organ. Cartilage, the smooth tissue that helps bones glide, becomes damaged over time. At the same time, the bone under the cartilage can harden and remodel, small bony outgrowths called osteophytes can form, and the synovium may become mildly inflamed. Muscles around the joint may weaken, which can worsen pain and instability.

This process is influenced by both mechanical and biological factors. Mechanical factors include excess body weight, malalignment, repetitive occupational or sports stress, and previous injuries such as meniscal tears or ligament damage. Biological factors include ageing-related tissue changes, genetics, and inflammatory signaling within the joint.

OA is often divided into two broad types:

1. Primary OA: develops without a single obvious cause, usually related to age, genetics, and cumulative joint stress.
2. Secondary OA: develops after a clear trigger such as trauma, congenital joint abnormality, inflammatory arthritis, or metabolic disease.

Pain in OA does not come from cartilage alone, because cartilage has no nerves. Pain likely arises from bone, synovium, ligaments, joint capsule, and surrounding muscles, which helps explain why symptoms and X-ray findings do not always match closely.

Evidence and uses

For a condition like OA, the key question is not what it is "used for" but how it is managed and what treatments have evidence. There is no proven disease-modifying medicine that reliably reverses or stops typical osteoarthritis in routine clinical practice. Treatment aims to reduce pain, improve function, and maintain mobility.

The best-supported first-line measures are:

1. Exercise: strengthening, aerobic activity, and range-of-motion work improve pain and function. For knee and hip OA, exercise is one of the most consistently recommended treatments.
2. Weight loss when relevant: in people with overweight or obesity, even modest weight reduction can reduce load on weight-bearing joints and improve symptoms.
3. Education and self-management: learning pacing, joint protection, and realistic activity goals helps many people stay active.
4. Physical therapy and assistive devices: targeted therapy, braces, canes, and footwear changes may help selected patients.

Medicines may help symptoms but do not cure OA. Options commonly used include topical NSAIDs, oral NSAIDs when appropriate, and sometimes short-term analgesics. Intra-articular corticosteroid injections can provide temporary relief for some people, especially with knee OA. Evidence for hyaluronic acid injections is mixed, and recommendations vary by guideline.

Surgery, especially joint replacement, is considered when pain and disability remain severe despite non-surgical treatment. Knee and hip replacement can substantially improve quality of life in carefully selected patients.

In India, OA is a common cause of pain and mobility limitation in older adults, and practical management often includes weight control, quadriceps strengthening for knee OA, walking aids when needed, and attention to coexisting diabetes or cardiovascular disease before using long-term pain medicines.

Diagnosis / how it's measured

OA is usually diagnosed clinically, based on symptoms, examination, and sometimes imaging. Common symptoms are activity-related joint pain, short-lived morning stiffness, stiffness after sitting, creaking or grinding, and reduced movement. Swelling may occur, especially in the knee.

Doctors look for tenderness, reduced range of motion, bony enlargement, crepitus, malalignment, and difficulty with walking or rising from a chair. The diagnosis is often straightforward in older adults with typical symptoms.

Tests that may be used include:

Test	What it can show	Limits
X-ray	Joint-space narrowing, osteophytes, bone changes	Symptoms may be worse or milder than the X-ray suggests
MRI	Cartilage, meniscus, bone marrow, soft tissues	Usually not needed for routine OA diagnosis
Blood tests	Helps rule out inflammatory arthritis or gout	No blood test confirms typical OA

Imaging is not always necessary if the presentation is classic. Blood tests are mainly used when another diagnosis is possible, such as rheumatoid arthritis, infection, or crystal arthritis.

When to see a clinician

See a clinician if joint pain, stiffness, or swelling lasts more than a few weeks, limits daily activities, or keeps returning. Medical review is also important if pain follows an injury, the joint locks or gives way, or walking becomes difficult.

Urgent assessment is needed if a joint is hot, very swollen, red, or associated with fever, because infection or crystal arthritis may need prompt treatment. Seek care sooner if you have unexplained weight loss, severe night pain, or rapidly worsening symptoms.

People with OA should also discuss treatment choices if they need frequent pain medicines, because NSAIDs can raise the risk of stomach bleeding, kidney injury, and blood pressure problems in some patients. A clinician can help balance symptom relief with safety.

Limitations and open questions

OA is common, but there are still important gaps in care and research. One limitation is that structural damage on imaging does not always predict pain severity or disability. Another is that OA is not one single disease process; knee OA after sports injury may differ biologically from hand OA in later life.

Evidence is strong for exercise, weight management, and joint replacement in selected patients, but many proposed disease-modifying treatments have not yet shown clear real-world benefit. Research is ongoing on earlier diagnosis, better pain phenotyping, and treatments that target inflammation, bone remodeling, or cartilage repair.

There is also growing interest in whether some OA changes may be partly reversible in specific settings, but this remains an evolving area rather than established clinical practice. If symptoms are persistent or treatment is not helping, reassessment matters because pain may reflect OA plus another condition such as bursitis, referred spine pain, or inflammatory arthritis.