Building up knee?

[Keith]

I'm having trouble with my knee. About 4 days ago, I bent it to ~90 degrees with my body weight on it (ie. I sat down) it suddenly hurt a lot (the pain feels like it's inside the joint). I gave it a couple of days to recover, during which time it didn't trouble me at all (walking, jogging, carrying heavy bags etc.) except when I did that movement again - which immediately hurt it again.

So my question is: How do I build up the muscles to support that knee when flexing it with weight on (ie. engaging in resistance training such as squats and lunges) causes it to spazz out? I do an hour workout a couple of times a week and would like to be able to participate in that fully.

Thanks.

P.S. I'm carrying rather a lot of extra weight. Obviously, I'm working to get that down as well.

[SmellyOrc]

Improve ankle and hip flexibility and mobility, lose the extra weight, and you should be fine.
Pavel Tsatsouline's 'Relax Into Stretch' and 'Super Joints' should help you out here.