Osteochondritis dissecans (OCD) is a joint disorder in which cracks form in the articular cartilage and the underlying subchondral bone. It is caused by blood deprivation in the subchondral bone, which leads to death of subchondral bone tissues in a process called avascular necrosis. The bone is then reabsorbed by the body, leaving the articular cartilage it supported prone to damage. The result is fragmentation of both cartilage and bone, and the free movement of these osteochondral fragments within the joint space, causing pain and further damage. In humans, OCD is a rare disease, occurring in only 15 to 30 people per 100,000 in the general population each year. Although rare, it is an important cause of joint pain in physically active adolescents. As their bones are still growing, adolescents are more likely than adults to recover from OCD, attributable to the growing bone's ability to repair damaged or dead bone tissue and cartilage in a process called bone remodeling. While OCD may affect any joint, the knee tends to be the most commonly affected, and constitutes 75% of all cases.

Read the rest of this article: http://en.wikipedia.org/wiki/Osteochondritis_dissecans

_______________________________ Today's selected anniversaries:

1868:

Astronomer Pierre Janssen discovered helium while analyzing the chromosphere of the sun during a total solar eclipse in Guntur, India. http://en.wikipedia.org/wiki/helium

1877:

Asaph Hall discovered Phobos , the larger of Mars' two moons, six days after discovering Deimos, the other one. http://en.wikipedia.org/wiki/Phobos_%28moon%29

1920:

The Nineteenth Amendment to the United States Constitution was ratified, guaranteeing women's suffrage in that country. http://en.wikipedia.org/wiki/Women%27s_suffrage_in_the_United_States

1948:

Australia completed a 4–0 Ashes series win, earning them the nickname of "The Invincibles" for being the first Test cricket match side to play an entire tour of England without losing a match. http://en.wikipedia.org/wiki/Fifth_Test%2C_1948_Ashes_series

1966:

Vietnam War: Members from D Company of the 6th Battalion of the Royal Australian Regiment were surrounded and attacked on all sides by a much larger Viet Cong unit at the Battle of Long Tan, but held them off for several hours until reinforcements arrived. http://en.wikipedia.org/wiki/6th_Battalion%2C_Royal_Australian_Regiment

1989:

Leading Colombian presidential hopeful Luis Carlos Galán was assassinated during a public demonstration in the town of Soacha, Cundinamarca. http://en.wikipedia.org/wiki/Luis_Carlos_Gal%C3%A1n

_____________________________ Wiktionary's word of the day:

ness (n): (geography) A promontory; a cape or headland http://en.wiktionary.org/wiki/ness

___________________________ Wikiquote quote of the day:

Tho' the world could turn from you,

This, at least, I learn from you: Beauty and Truth, tho' never found, are worthy to be sought,

The singer, upward-springing,   Is grander than his singing,   And tranquil self-sufficing joy illumes the dark of thought. --Robert Williams Buchanan http://en.wikiquote.org/wiki/Robert_Williams_Buchanan