Arthritis & Rheumatism

Q&A: Evaluation can determine cause, guide treatment for knee pain

Dear Mayo Clinic: One year ago, I fell and broke my arm. While my arm has healed, my knees also have been bothering me since I fell. I have arthritis in both knees and a slight tear in the meniscus on one knee, but both knees ...

Arthritis & Rheumatism

Q&A: Evaluation can determine cause, guide treatment for knee pain

Dear Mayo Clinic: One year ago, I fell and broke my arm. While my arm has healed, my knees also have been bothering me since I fell. I have arthritis in both knees and a slight tear in the meniscus on one knee, but both knees ...

Arthritis & Rheumatism

Researcher evaluates estrogen as therapy for knee osteoarthritis

More than 30 million Americans suffer from osteoarthritis of the knee, according to the Centers for Disease Control and Prevention. The degenerative joint disease, often caused by wear and tear, is a leading cause of disability ...

Surgery

3-D-printable implants may ease damaged knees

A cartilage-mimicking material created by researchers at Duke University may one day allow surgeons to 3-D print replacement knee parts that are custom-shaped to each patient's anatomy.

Surgery

Study finds knee surgery holds even in heavier patients

Meniscal repairs are one of the most common orthopedic surgeries in the U.S., but about 15 percent of them fail, requiring the patient to undergo a second surgery. Many have assumed that an increased body mass index (BMI) ...

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Meniscus

The meniscus (plural: menisci, from the Greek for "crescent") is the curve in the upper surface of a liquid close to the surface of the container or another object, caused by surface tension. It can be either convex or concave. A convex meniscus occurs when the molecules have a stronger attraction to each other (cohesion) than to the material of the container (adhesion). This may be seen between mercury and glass in barometers and thermometers. One can over-fill a glass with mercury and produce a convex meniscus that rises above the top of the glass. Conversely, a concave meniscus occurs when the molecules of the liquid attract those of the container's, causing the surface of the liquid to cave downwards. This can be seen in a glass of water.

Capillary action acts on concave menisci to pull the liquid up, increasing favorable contact area between liquid and container, and on convex menisci to pull the liquid down, reducing the amount of contact area. This phenomenon is important in transpirational pull in plants. Honey, water, milk etc. have a lower meniscus. When a tube of a narrow bore, often called a capillary tube, is dipped into a liquid and the liquid wets the tube (with zero contact angle), the liquid surface inside the tube forms a concave meniscus, which is a virtually spherical surface having the same radius, r, as the inside of the tube. The tube experiences a downward force of magnitude 2πrdσ[citation needed].

When reading a scale on the side of an instrument filled up with liquid, the meniscus must be taken into account in order to obtain a precise measurement. Manufacturers take the meniscus into account and calibrate their measurement marks relative to the resulting meniscus. The measurement is taken with the meniscus at eye level to eliminate parallax error, and at the center of the meniscus, i.e. the top of a convex meniscus, or the bottom of a concave meniscus. This means that the instrument is calibrated for one specific fluid, usually water.

This text uses material from Wikipedia, licensed under CC BY-SA