Knee Osteoarthritis: Understanding the Pain

Pain that develops gradually

Unlike a sprain or a sports injury, knee osteoarthritis does not usually begin with one specific incident. It tends to develop gradually: stiffness in the morning, discomfort after a long walk, then pain that becomes increasingly present in everyday life.

This gradual progression can sometimes delay diagnosis and leaves a simple question that is rarely explained clearly: why, exactly, does it hurt?

What is knee osteoarthritis?

Knee osteoarthritis involves progressive changes to the cartilage covering the ends of the bones in the joint, accompanied by changes in the underlying bone. It is one of the most common joint conditions in adults.

According to Physioswiss, around 6% of adults have clinically apparent symptoms of knee osteoarthritis, with similar figures expected in Switzerland. By comparison, around one-third of the adult population shows signs of osteoarthritis on X-rays.

Why does osteoarthritis hurt?

Cartilage itself is not innervated: it contains no nerve endings and therefore cannot, strictly speaking, transmit pain. Osteoarthritis pain arises from other structures within and around the joint that do contain nerves, including the subchondral bone, synovial membrane, joint capsule, ligaments and surrounding tissues.

Depending on the joint and the individual, these structures may also be affected by local inflammatory processes alongside mechanical stresses.

Deposits of calcium-containing crystals can also be present in joints affected by osteoarthritis. These calcifications, including basic calcium phosphate and calcium pyrophosphate crystals, are studied for their role in inflammatory and degenerative processes within the joint. They are not present to the same extent in every person with osteoarthritis.

This also helps explain why the severity seen on an X-ray, which mainly reflects structural changes within the joint, does not always predict how much pain someone experiences. Some people with advanced osteoarthritis on imaging have relatively little discomfort, while others with more subtle changes experience considerably more pain.

Pain is also influenced by factors such as muscle strength around the joint, walking stability and individual sensitivity.

Factors that can contribute to knee osteoarthritis

Several factors repeatedly appear: age, genetic predisposition, excess weight, which increases mechanical load on the knee while also being associated with broader inflammatory processes, repeated stress on the joint through certain occupations or sports, and a history of knee injury.

None of these factors determines the course on its own. They combine differently in each individual situation.

Recommended first-line measures

Adapted movement and muscle strengthening are among the recommended first-line measures for knee osteoarthritis.

Contrary to a common misconception, prolonged rest is generally not the answer.

Looking beyond the joint

The possible presence of calcifications and the local environment of the joint are also factors I consider depending on the individual situation.

Where can percutaneous hydrotomy fit?

At Centre Algos, percutaneous hydrotomy is one of the treatments used for knee osteoarthritis.

The treatment can aim to improve pain, mobility and function while supporting the local tissue environment through hydration and targeted therapeutic support. Clinical and structural observations have also generated interest in its regenerative potential in degenerative joint conditions.

Hydrotomy can be integrated with exercise, movement, load management and other appropriate treatments according to the individual clinical picture.

Learn more about Percutaneous Hydrotomy for Knee Osteoarthritis or explore the Percutaneous Hydrotomy treatment at Centre Algos.

When to seek advice

An earlier diagnosis generally provides more opportunities to address the factors involved.

Sources and further reading

• Physioswiss, Factsheet: knee osteoarthritis (in French), on prevalence, risk factors and conservative management.

• Swiss Federal Office of Public Health / MonAM, Osteoarthritis, arthritis and osteoporosis (in French), official Swiss statistics on the frequency of joint conditions.

• Rosenthal AK, "Crystals, inflammation, and osteoarthritis", Current Opinion in Rheumatology, 2011;23(2):170-173, doi:10.1097/BOR.0b013e3283432d1f, a peer-reviewed review on the presence of calcium-containing crystals (calcium pyrophosphate and basic calcium phosphate) in osteoarthritic joints and their studied role in inflammatory and degenerative processes.

These resources provide further detail on the mechanisms, prevalence data and management recommendations mentioned above.

Frequently asked questions

Does osteoarthritis on an X-ray necessarily mean severe pain?

Not necessarily. Because cartilage itself is not innervated, pain arises mainly from other structures within the joint and the surrounding tissues. The severity of changes visible on imaging and the intensity of pain therefore do not always correspond.

Is knee osteoarthritis only related to age?

No. Age is an important factor, but weight, previous injuries, genetics and certain occupational or sporting demands also play a role, sometimes in younger people.

Should I avoid movement if I have knee osteoarthritis?

No, quite the opposite. Muscle strengthening and maintaining an appropriate level of activity are among the first-line measures recommended to reduce pain and preserve joint function. Prolonged rest is generally not the solution.

Is knee replacement always necessary?

No. Surgery is not automatically required. Conservative approaches are recommended first. The decision depends on the stage of osteoarthritis, its impact on everyday function and the response to measures already tried, and should be made together with an appropriate specialist.

What is happening in your case?

This article describes general mechanisms and factors. What is causing your knee pain in your particular situation deserves an examination and a real conversation rather than a generic answer.

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