A knee that has been manageable for weeks or months can suddenly become painful, swollen, and stiff. This is often called an arthritis flare. Flares may follow extra walking, stairs, travel, yard work, a new exercise program, or no obvious trigger at all.
The good news is that many flares settle with a short period of focused treatment. The important part is knowing what you can safely do at home, when an injection or medication may help, and which symptoms suggest something more urgent than routine osteoarthritis.
What is a knee arthritis flare?
Knee osteoarthritis develops when the joint surface becomes worn and the tissues around the knee become irritated. During a flare, inflammation increases and the knee may temporarily become more painful than usual.
Common symptoms include:
- Increased aching with standing or walking
- Swelling or a feeling of pressure inside the knee
- Stiffness after sitting or first thing in the morning
- Reduced bending or difficulty fully straightening the knee
- Pain with stairs, getting out of a chair, or walking downhill
- A warm feeling around the joint
- More pain at night
A flare does not always mean that the arthritis has suddenly become dramatically worse. Sometimes the knee is simply reacting to more load than it was ready to tolerate.
What should I do during the first 48 to 72 hours?
The first goal is to calm the knee without becoming completely inactive.
Reduce the activity that triggered the flare
Temporarily cut back on long walks, repeated stairs, deep squats, kneeling, and high-impact exercise. This is relative rest, not strict bed rest. Short, comfortable walks around the home are usually better than staying still all day.
Use cold therapy
A cold pack or ice machine may help reduce pain and swelling. Apply cold for about 15 to 20 minutes at a time, with a cloth between the skin and the cold source. Repeat several times during the day as needed.
Elevate the leg
When resting, support the leg so the knee is above the level of the heart when practical. Support under the calf and ankle rather than keeping a pillow directly behind the knee for long periods, especially if the knee is already becoming difficult to straighten.
Consider compression
A simple elastic knee sleeve may provide comfort and reduce mild swelling. It should feel supportive, not tight. Remove it if you notice numbness, tingling, increased pain, or swelling below the sleeve.
Keep the knee moving gently
Comfortable range-of-motion exercises can prevent the knee from becoming increasingly stiff. Avoid forcing the knee through sharp pain. Gentle motion should help maintain function without provoking a larger inflammatory response.
Which medications may help?
Medication choices depend on your medical history, kidney function, stomach history, blood pressure, blood thinners, allergies, and other prescriptions.
Topical anti-inflammatory medication
A topical anti-inflammatory gel may help localized knee pain with less whole-body exposure than an oral medication. It still has precautions, so follow the label and your clinician’s advice.
Oral anti-inflammatory medication
Medications such as ibuprofen, naproxen, or prescription anti-inflammatories may reduce pain and swelling. These are not appropriate for everyone, particularly patients with kidney disease, ulcers, certain heart conditions, uncontrolled blood pressure, or some blood-thinner regimens.
Acetaminophen
Acetaminophen may help pain, although it does not directly reduce inflammation. Avoid exceeding the recommended daily dose and account for acetaminophen that may already be included in combination medications.
Short oral steroid course
For selected patients, a short course of oral steroids may help settle a significant inflammatory flare. This requires individualized medical guidance, especially for patients with diabetes, stomach irritation, infection risk, or other medical concerns.
Do not start or combine medications based only on internet advice. A quick review of your medication list can prevent avoidable complications.
When should I call the orthopedic office?
Contact the orthopedic team when:
- Pain is not improving after several days of activity modification and home care
- Swelling is substantial or repeatedly returns
- The knee is becoming harder to bend or straighten
- You are limping more or relying on a cane unexpectedly
- Pain is interfering with sleep or basic daily activities
- You are unsure whether symptoms are from arthritis, a meniscus problem, a tendon, gout, or another cause
- You need guidance on medication safety
Pacific Bone & Joint evaluates knee pain in Honolulu and on Hawaiʻi Island. Depending on the situation, the visit may include an examination, weight-bearing X-rays, ultrasound, or other testing.
Can an injection calm a flare?
Injections can be useful when symptoms are not settling with simpler measures.
Cortisone injection
A corticosteroid injection can reduce inflammation and may provide relatively quick relief. It is often considered when the knee is swollen and painful enough to limit walking or sleep. The duration of benefit varies, and repeated injections should be used thoughtfully.
Hyaluronic acid injection
Hyaluronic acid is intended to improve joint lubrication and may help selected patients with knee osteoarthritis. It is generally not the fastest option for an acute flare, but it can be part of a broader nonsurgical treatment plan.
Platelet-rich plasma
Platelet-rich plasma, or PRP, uses a concentrated portion of the patient’s own blood. Some patients with mild to moderate osteoarthritis may consider PRP as part of a joint-preservation strategy. It is not appropriate for every patient, and expected benefit depends on the severity and pattern of arthritis.
Aspiration of fluid
When the knee is significantly swollen, removing fluid may improve pressure and help determine whether the swelling is from osteoarthritis, crystals such as gout, blood, or infection. Fluid may be sent for laboratory analysis when needed.
Could this be something other than arthritis?
Not every painful, swollen knee is a routine arthritis flare.
Other possible causes include:
- Meniscus injury, particularly with catching or locking
- Gout or pseudogout
- Tendon or bursa irritation
- Stress fracture
- Ligament injury
- Infection
- A blood clot in the leg
- Referred pain from the hip or lower back
A careful history and examination usually narrow the possibilities quickly.
Warning signs that need prompt evaluation
Seek urgent medical attention for:
- Fever with a hot, very swollen knee
- Rapidly increasing redness
- Inability to bear weight after an injury
- A locked knee that cannot bend or straighten
- New calf swelling, chest pain, or shortness of breath
- Sudden severe pain after a fall or twisting injury
- Drainage from a surgical incision
These symptoms are not typical of an uncomplicated arthritis flare.
What happens after the flare settles?
Once pain and swelling improve, return to activity gradually. Increasing too quickly often recreates the same problem.
A longer-term arthritis plan may include:
- Strengthening the muscles around the knee and hip
- Low-impact aerobic exercise
- Weight management when appropriate
- Bracing for selected alignment patterns
- Anti-inflammatory strategies
- Injections
- Physical therapy
- Joint-preservation procedures in selected patients
- Knee replacement when arthritis becomes advanced and quality of life is significantly affected
For patients already preparing for surgery, our week-by-week knee replacement recovery guide explains what to expect after the procedure.
The practical takeaway
When knee arthritis suddenly flares, reduce the activity that triggered it, use cold therapy, elevate the leg, keep the joint moving gently, and review medication options safely. If the knee is not improving, is repeatedly swelling, or is limiting basic function, an orthopedic evaluation can help identify the cause and calm the flare more efficiently.
To schedule an evaluation with Pacific Bone & Joint, contact our team. We care for patients in Honolulu and on Hawaiʻi Island and can help build a treatment plan that fits the severity of your arthritis, your activity goals, and your overall health.
