Patient case (clinical description): A 47-year-old woman comes to the office complaining of pain in the calf and knee when she bends down. The pain limits her activity. Her medical history is significant for osteoarthritis, for which she uses nonsteroidal anti-inflammatory drugs (NSAIDs) for the past two years. She is living with her husband and has 3 children. She doesn't smoke but drinks alcohol occasionally. Her vital signs are normal. On physical examination, there is a small effusion in the right knee. The effusion grew a little larger and she developed a tender swelling in the popliteal fossa and calf. Both the pain and swelling worsened as she bent and straightened her knee.

Patient's own account: I'm a 47-year-old woman, married with 3 kids. I don't smoke and I drink occasionally. I went to the doctor because of pain in my calf and knee when I was bending down. This has been limiting my daily activities. I have been diagnosed with osteoarthritis for which I have taken anti-inflammatory drugs for the past 2 years. The doctor saw a small fluid buildup in my right knee. This buildup became a bit bigger and I have a swollen calf. The pain is worse when I bend and straighten my knee.

Clinical trial: To Look at the Characteristics of Synovial Fluid and Cartilage Matrix in Osteoarthritic Knee After Hyaluronic Acid Injection

Eligibility criteria:
Inclusion Criteria:

          -  Age 18 to 80 years

          -  Symptomatic knee OA as defined by the American College of Rheumatology criteria

          -  Kellgren-Lawrence grade I, II or III on prior x-rays (take within 6 months of
             screening visit)

          -  knee pain score >40 mm on a 100 mm visual analogue scale for > 15 days in the last
             month

          -  NSAIDs permitted if the dose has been stable for at least one month prior to baseline
             and stays stable during the study

          -  Have been recommended for Euflexxa treatment by physician

          -  Knee effusion based on clinical exam or imaging

        Exclusion Criteria:

          -  Any contraindication to MRI (pregnancy, metallic fragments in the eyes, vascular
             clips, Pacemakers etc)

          -  History of knee replacement

          -  Known sensitivity or allergy to any component of Euflexxa

          -  Inflammatory arthritis

          -  Previously received viscosupplementation therapy within 6 months of study enrollment

          -  Intra-articular injection of corticosteroid to study joint within the past 3 months

          -  Arthroscopic or open surgery within the previous 12 months or planned surgery to the
             study joint

          -  Concomitant medications of oral/parenteral corticosteroids

          -  Morbid obesity defined as body mass index (BMI) >40 kg/m2

          -  Active malignancy; an active systemic infection; recent high impact or high energy
             trauma (clinically defined) to the study joint

          -  Large knee effusion based on clinical exam or imaging
No condition on gender to be admitted to the trial.
No healthy subjects accepted to join the trial.
Subject must be at least 18 Years old.
Subject must be at most 80 Years

Eligibility (NLI label): Entailment