Knee injections are commonly used to reduce pain, calm inflammation, remove excess fluid, or help clarify where symptoms are coming from. But “a knee injection” is not one single treatment. The medication, target, diagnosis, timing, and method of placement all matter.
An ultrasound-guided knee injection allows the clinician to see the needle, joint space, fluid, tendons, blood vessels, and other nearby structures in real time. The goal is not simply to use more technology. It is to make sure the procedure has a clear purpose and that the medication or aspiration reaches the intended target.
From my perspective as an orthopedic surgeon, the most useful questions are:
- What is causing the pain?
- Is the target the knee joint, a bursa, a cyst, or a tendon region?
- What are we injecting, and what does the evidence actually show?
- How will the result affect the next step in treatment?
Why use ultrasound for a knee injection?
Many knee injections can be performed using surface landmarks. However, studies consistently show that ultrasound guidance improves the accuracy of intra-articular knee injections.
A 2021 systematic review of randomized trials found that ultrasound-guided knee injections were more accurate than landmark-guided injections across the evaluated approaches. A newer systematic review reported cumulative accuracy of about 95% with ultrasound guidance compared with about 82% using landmarks alone. Read the 2021 systematic review and the 2026 systematic review.
A 2024 meta-analysis also found that ultrasound-guided injections were associated with better patient-reported pain, function, and satisfaction outcomes than landmark-guided injections in osteoarthritis trials. That does not mean ultrasound guarantees relief. It means accurate placement may improve the chance that the intended treatment is delivered correctly. Read the meta-analysis.
Ultrasound guidance may be particularly helpful when:
- The knee has significant swelling
- The anatomy is difficult to palpate
- A prior landmark-guided injection did not help
- The target is a bursa, cyst, tendon sheath, or specific soft-tissue structure
- Fluid needs to be aspirated
- The clinician wants to avoid visible blood vessels or other nearby structures
- The diagnosis is uncertain and the ultrasound examination may provide useful additional information
What conditions may be treated or evaluated?
Knee osteoarthritis
Knee osteoarthritis can cause pain, stiffness, swelling, reduced motion, difficulty with stairs, and aching after activity. An injection may be considered when exercise, weight management, topical medication, oral medication, bracing, or physical therapy has not provided enough relief.
The American College of Rheumatology and Arthritis Foundation strongly recommend intra-articular corticosteroid injections as an option for knee osteoarthritis because they can provide short-term symptom relief. They should be used as part of shared decision-making and not as a substitute for strengthening, activity modification, or a broader arthritis plan. Read the ACR/Arthritis Foundation guideline.
Learn more about knee arthritis treatment options.
Knee swelling or joint effusion
A swollen knee may contain excess joint fluid. Aspiration, also called arthrocentesis, removes fluid with a needle.
Aspiration may be useful to:
- Reduce pressure and discomfort
- Improve the accuracy of a subsequent injection
- Evaluate for crystals such as gout or pseudogout
- Evaluate for infection when clinically suspected
- Help determine whether the swelling is truly inside the joint
When infection is a concern, fluid analysis is more important than simply injecting medication. A painful, hot, rapidly swollen knee with fever requires prompt medical evaluation.
Baker’s cyst
A Baker’s cyst is a fluid-filled structure behind the knee that often communicates with the knee joint. It commonly develops because the knee is producing excess fluid from arthritis, a meniscus problem, or inflammation.
Ultrasound can confirm the cyst, assess its size, and help distinguish it from other causes of a lump behind the knee. In selected cases, the cyst may be aspirated under ultrasound guidance. However, treating the cyst alone may not prevent recurrence if the underlying knee problem continues to produce fluid.
Read our detailed guide to Baker’s cysts behind the knee.
Bursitis and tendon-related pain
Pain near the knee does not always come from inside the joint. Ultrasound can help evaluate and target structures such as:
- The pes anserine bursa on the inner side of the knee
- The prepatellar bursa over the kneecap
- The infrapatellar bursae below the kneecap
- The quadriceps or patellar tendon region
- The iliotibial band region on the outer knee
Corticosteroid should not be injected directly into a tendon. Tendon pain is often better treated with progressive strengthening, load management, and correction of contributing mechanics.
Meniscus symptoms
A knee injection does not repair a torn meniscus. It may reduce inflammation in an arthritic knee that also has a degenerative meniscus tear, but it does not restore the torn tissue.
The key distinction is whether symptoms are mainly from arthritis and inflammation or from a mechanically unstable tear causing true locking or persistent focal symptoms.
What medications may be injected?
Corticosteroid, or cortisone
Corticosteroid is an anti-inflammatory medication. It may reduce pain and swelling for a limited period, especially during an arthritis flare or when inflammation is preventing participation in therapy.
Important points:
- Relief is usually temporary
- It does not regrow cartilage
- It does not reverse arthritis
- It may temporarily raise blood sugar
- Repeated injections should not become an automatic long-term cycle
- Timing matters when knee replacement is being considered
Potential risks include infection, bleeding, temporary pain flare, skin or fat changes at superficial sites, elevated blood sugar, and possible cartilage-related concerns with repeated exposure.
Hyaluronic acid, or “gel” injections
Hyaluronic acid injections are intended to improve joint lubrication and reduce symptoms. The evidence is mixed, and guidelines do not all reach the same conclusion.
The American Academy of Orthopaedic Surgeons does not recommend routine use of hyaluronic acid injections for symptomatic knee osteoarthritis based on the average results in the available evidence. Some clinicians and patients still consider them in selected situations because individual responses vary and the safety profile is generally acceptable. This is a preference-sensitive decision rather than a guaranteed treatment. Read the AAOS knee osteoarthritis guideline.
Platelet-rich plasma
Platelet-rich plasma, or PRP, is prepared from a patient’s blood and contains a concentrated platelet fraction. Evidence for knee osteoarthritis is evolving.
Some randomized trials and meta-analyses report improvements in pain and function in selected patients, while major guidelines differ because PRP preparation methods, dosing, patient selection, and study quality vary. PRP should not be described as proven cartilage regrowth or a guaranteed way to avoid knee replacement.
From a clinical perspective, PRP is most reasonable to discuss when the diagnosis is clear, expectations are realistic, and the patient understands that insurance coverage and treatment response may vary.
Learn more about regenerative medicine options.
Local anesthetic
Local anesthetic may be used to reduce procedural discomfort or as part of a diagnostic injection. Temporary improvement can help determine whether the targeted structure is contributing to pain.
A diagnostic response is one piece of information. It must still be interpreted together with the examination, X-rays, MRI findings, activity pattern, and overall clinical picture.
What happens during the procedure?
A typical ultrasound-guided knee injection or aspiration includes:
- Review of the diagnosis, medications, allergies, and purpose of the procedure
- Positioning the knee to expose the intended target
- Ultrasound examination of the joint and surrounding structures
- Cleaning the skin with antiseptic solution
- Use of sterile supplies and sterile ultrasound technique as appropriate
- Local numbing medication when needed
- Real-time visualization of the needle as it approaches the target
- Aspiration of fluid, injection of medication, or both
- A brief observation period and post-procedure instructions
Most patients feel pressure, a pinch, or brief soreness. A large fluid aspiration may provide immediate pressure relief, although the underlying condition still needs treatment.
How should I prepare?
Tell the clinical team about:
- Blood thinners or a bleeding disorder
- Diabetes
- Medication allergies
- Fever, infection, antibiotics, or an open wound
- Pregnancy or possible pregnancy
- Previous reactions to injections
- Recent or planned surgery
- Previous knee injections and how long they helped
Do not stop prescription blood thinners unless the prescribing clinician and procedural clinician provide specific instructions.
What should I expect afterward?
After the procedure:
- The knee may feel numb for several hours if anesthetic was used
- Mild soreness or a temporary steroid flare may occur
- Blood sugar may rise temporarily after corticosteroid
- Strenuous activity may be limited briefly
- Ice may be used according to the instructions provided
- A symptom diary can be useful after a diagnostic injection
Contact the office promptly for increasing redness, drainage, fever, rapidly worsening swelling, severe pain, or new weakness.
How long does relief last?
There is no universal answer. Relief depends on:
- The accuracy of the diagnosis
- The medication used
- The severity of arthritis
- Whether the pain is coming from more than one structure
- Activity demands
- Strength and movement patterns
- Participation in physical therapy or exercise
An injection that does not help can still provide useful information. It may suggest that the targeted structure was not the main pain generator or that the underlying condition is too advanced for an injection to provide meaningful relief.
How often can knee injections be repeated?
There is no single schedule that is appropriate for every patient.
Repeated injections should be reconsidered when:
- Each injection helps for a shorter period
- The diagnosis has not been reassessed
- Weakness, instability, or loss of motion is worsening
- Advanced arthritis is substantially limiting daily life
- Surgery is being considered
- The patient is relying on injections instead of rehabilitation or other appropriate treatment
European recommendations emphasize individualized decision-making, appropriate aseptic technique, and consideration of medical conditions, prior response, and surgical timing. Read the EULAR recommendations.
Can an injection delay knee replacement?
An injection may reduce symptoms temporarily, but it does not reverse advanced arthritis. Some patients use an injection to manage a flare, complete an important event, participate in therapy, or gain time before surgery.
When pain, stiffness, sleep disruption, and loss of function remain severe despite reasonable nonsurgical treatment, continuing a cycle of short-lived injections may be less useful than discussing knee replacement.
Injection timing before joint replacement matters because intra-articular corticosteroid injections close to surgery may influence infection-risk discussions. The operating surgeon should know the date, medication, and location of every recent injection.
Dr. Morton’s perspective
Ultrasound guidance improves precision, but precision is only one part of good care.
A useful knee injection should have a specific goal:
- Reduce an inflammatory flare
- Remove and analyze excess fluid
- Target a clearly identified bursa or cyst
- Help confirm the pain source
- Create a window for strengthening and rehabilitation
- Provide temporary symptom control while a longer-term decision is made
The best treatment depends on whether the problem is mild arthritis, advanced bone-on-bone disease, a meniscus problem, tendon overload, instability, infection, gout, or another diagnosis. These conditions should not all receive the same injection simply because the knee hurts.
Ultrasound-guided knee care in Hawai‘i
Pacific Bone & Joint evaluates knee arthritis, swelling, meniscus symptoms, sports injuries, Baker’s cysts, tendon problems, and persistent knee pain. Care is available in Honolulu, Waipahu, Hilo, and Kona by appointment.
Evaluation may include examination, X-rays, musculoskeletal ultrasound, MRI review, physical therapy, aspiration, image-guided injection, regenerative medicine discussion, or surgical consultation when appropriate.
Call (808) 439-6201 to request an appointment.
This article is educational and does not replace an individualized examination.
Sources and further reading
- Kolasinski SL, et al. 2019 American College of Rheumatology/Arthritis Foundation Guideline for the Management of Osteoarthritis of the Hand, Hip, and Knee. Arthritis Care & Research. 2020.
- American Academy of Orthopaedic Surgeons. Management of Osteoarthritis of the Knee, Third Edition. AAOS Clinical Practice Guideline. 2021.
- Fang WH, et al. Ultrasound-Guided Knee Injections Are More Accurate Than Blind Injections: A Systematic Review of Randomized Controlled Trials. Arthroscopy, Sports Medicine, and Rehabilitation. 2021.
- Kasitinon D, et al. Accuracy and Efficacy of Intra-articular Knee Injections/Aspirations Under Ultrasound Versus Landmark Guidance: A Systematic Review. American Journal of Physical Medicine & Rehabilitation. 2026.
- Oo WM, et al. Comparison of Ultrasound Guidance With Landmark Guidance for Symptomatic Benefits in Knee, Hip and Hand Osteoarthritis: Systematic Review and Meta-analysis of Randomised Controlled Trials. Australasian Journal of Ultrasound in Medicine. 2024.
- Uson J, et al. EULAR Recommendations for Intra-Articular Therapies. Annals of the Rheumatic Diseases. 2021.
