Knee pain is a common condition that can have 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:
Osteoarthritis
This is the most common form of arthritis. Sudden knee pain without trauma can be the first sign of osteoarthritis. We generally 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.
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

Gout is a type of inflammatory arthritis that usually affects one joint at a time. Although it commonly affects the big joint, it can also affect the knee.
Acute inflammation occurs when high uric acid levels in the body concentrate on one joint. This causes a severe reaction, leading to pain and swelling. Generally, the knee joint is swollen and red from inflammation.
Gout is treated with medications such as ibuprofen or colchicine. In some cases, we suggest an ultrasound-guided cortisone injection. Diet and lifestyle factors, such as losing weight, drinking less alcohol, and avoiding foods such as sardines, anchovies, and mackerel, usually help reduce flare-ups.
Psoriatic arthritis

Psoriatic arthritis is an immune condition that affects the skin and joints, especially the knee. This condition causes swelling, pain, and redness in the knee joint. 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 and environmental factors are important. Not all people with psoriasis will develop psoriatic arthritis.
Treatment consists of anti-inflammatory medication such as ibuprofen, cortisone and immune drugs. A cortisone shot is sometimes needed to help with acute knee joint swelling.
Rheumatoid arthritis

Rheumatoid arthritis is an autoimmune disease in which the immune system attacks the synovial lining of joints. Unlike other inflammatory arthritis, this condition usually affects joints on both sides of the body.
While most cases develop slowly, 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.
Runners’ knees usually get worse after prolonged sitting, running, going up and down stairs, 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 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.
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