Plica syndrome is a condition that occurs when a plica (a vestigial extension of the protective synovial capsule of usually the knee) becomes irritated, enlarged, or inflamed. Cause
This inflammation is typically caused by the plica being caught on the femur, or pinched between the femur and the patella. The most common location of plica tissue is along the medial (inside) side of the knee. The plica can tether the patella to the femur, be located between the femur and patella, or be located along the femoral condyle. If the plica tethers the patella to the femoral condyle, the symptoms may cause it to be mistaken for chondromalacia. The plica themselves are remnants of the fetal stage of development where the knee is divided into three compartments. The plica normally diminish in size during the second trimester of fetal development, as the three compartments develop into the synovial capsule. In adults, they normally exist as sleeves of tissue called synovial folds. The plica are usually harmless and unobtrusive; plica syndrome only occurs when the synovial capsule becomes irritated, which thickens the plica themselves (making them prone to irritation/inflammation, or being caught on the femur). Diagnosis
If the plica tethers the patella to the femoral condyle, the symptoms may cause it to be mistaken for chondromalacia patellae. Diagnosis is often complicated by the thin structures of plicae, fenestrated septum or unfenestrated septum all being too fine to resolve well even in MRI. Treatment
Plica syndrome treatment focuses on decreasing inflammation of the synovial capsule.
This is easily determined by the height ratio of any object to the size of its shadow (if the height is measured vertical to the earths gravitational field, the projected shadow is ideally measured on a flat, level surface; furthermore, for objects wider than skulls or poles, the height and length are best measured relative to the same occluding edge). The greatest risk is at solar noon, when shadows are at their minimum and the suns radiation passes most directly through the atmosphere. Regardless of ones latitude (assuming no other variables), equal shadow lengths mean equal amounts of UV radiation. The skin and eyes are most sensitive to damage by UV at 265–275 nm wavelength, which is in the lower UVC band that is almost never encountered except from artificial sources like welding arcs. Most sunburn is caused by longer wavelengths, simply because those are more prevalent in sunlight at ground level. Ozone depletion
In recent decades, the incidence and severity of sunburn have increased worldwide, partly because of chemical damage to the atmospheres ozone layer. Between the 1970s and the 2000s, average stratospheric ozone decreased by approximately 4%, contributing an approximate 4% increase to the average UV intensity at the earths surface. Ozone depletion and the seasonal "ozone hole" have led to much larger changes in some locations, especially in the southern hemisphere. Tanning
Suntans, which naturally develop in some individuals as a protective mechanism against the sun, are viewed by most in the Western world as desirable.