Knee pain is a common condition that can be due to many causes. Sometimes, knee pain occurs after an injury or fall. In other cases, sudden knee pain might indicate a more severe problem, such as arthritis. So what causes sudden knee pain without injury, and how do we sort it out?

What causes sudden knee pain without injury? 

Sudden knee pain without injury can be caused by any one of the following:


This is the most common form of arthritis. Sudden knee pain without trauma can be the first sign of osteoarthritis. Generally, we think of it as a degenerative condition, although recent evidence suggests that inflammation plays an important role. In addition, degenerative meniscal tears are often part of the problem associated with early osteoarthritis.

Causes of osteoarthritis include acute knee injury, inactivity, and lifestyle factors such as diabetes and obesity.

Overall, treatment should improve lifestyle factors such as weight loss, exercise, and diet. Ibuprofen tablets can help in the short term. In more severe cases, hyaluronic acid or PRP injections can help.


gout in knee

Gout is a typical inflammatory arthritis that usually affects one joint at a time. Although it commonly affects the big joint, gout can also affect the knee.

Acute inflammation occurs when high uric acid levels in the body concentrate in one joint. This causes a severe reaction leading to pain and swelling. Generally, the knee joint is swollen and red from inflammation.

Treatment of gout consists of medications such as ibuprofen or colchicine. In some cases, we suggest an ultrasound-guided cortisone injection. Usually, diet and lifestyle factors, such as losing weight, drinking less alcohol, and avoiding foods such as sardines, anchovies, and mackerel, help reduce flares.

Psoriatic arthritis  

psoriatic arthritis in young female

Psoariatic arthritis is a type of immune condition that affects the skin and joints, especially in the knee. In the knee joint, this condition causes swelling, pain and redness. The skin rash is typically silvery grey or red  scaly spots that appear on the front of the knees or the tips of the elbows.

We’re not sure what causes psoriatic arthritis but genetic snad environmental factors are important. And not all people with psoriasis will go on to develop psoriatric arthritis.

Treatment consists of anti-inflamamtory medication such as ibuprofen, cortisone and immune drugs. Sometimes, a cortisone shot is needed to help with acute knee joint swelling.

Rheumatoid arthritis 

rheumatoid arthritis in knee

Rheumatoid arthritis is an autoimmune disease where the immune system attacks the synovial lining of joints. Compared to other inflammatory arthritis, this condition usually affects joints on both sides of the body.

While most cases develop slowly over time, some can suddenly occur with acute swelling.

Treatment of rheumatoid arthritis starts with ibuprofen tablets. In severe cases, we use steroids or immune drugs.

Runner’s knee  

Also known as patellofemoral pain syndrome or chondromalacia patella, this condition is caused by excessive pressure behind the knee cap, causing knee pain. Generally, the cause of runner’s knee is related to overuse and biomechanical factors that increase the forces behind the kneecap. These factors include muscle weakness of the thigh and buttock muscles, hamstring tightness, and flat feet.

Usually, runner’s knee gets worse after prolonged sitting, running, going up and downstairs, and kneeling. In addition, knee pain can occur suddenly, particularly after a long run.

Treatments consist of regular ice, ibuprofen tablets, and taping. In addition, physical therapy is essential to improve your knee and pelvis biomechanics, such as stretching, buttock strengthening, and changing your running shoes. Costine injections are rarely used and only if kneecap arthritis is also present.

How do we sort out a diagnosis of sudden knee pain without injury?

Often, we use blood tests to search for acute inflammation. Generally, we start with inflammatory markers such as CRP and ESR. These markers will be elevated in inflammation but will not tell us the exact type of arthritis. Also, not all people with active inflammatory arthritis will have raised inflammatory markers.

Also, we do serologic blood tests to help pin down the diagnosis. Examples include rheumatoid factor, anti-CCP, and ANA. Uric acid levels are helpful in gout. Genetic testing with HLA-B27 can help diagnose some types of arthritis.

Sometimes, we take a fluid sample from the knee joint to test for cells and crystals.

Finally, imaging can confirm the diagnosis of osteoarthritis. A plain X-ray or MRI of the knee is helpful in these cases.

Final word about sudden knee pain without injury

Sudden knee pain without injury requires expert attention to get the correct diagnosis. We suggest you see an expert sports medicine doctor who can confirm a diagnosis and get you on the proper treatment.

Sudden knee pain without injury: related conditions: 

Dr. Masci is a specialist sport doctor in London. 

He specialises in muscle, tendon and joint injuries.