You probably have a torn meniscus in your knee.
The knee joint has two pieces of semicircular cartilage on either side - these are called meniscus. These cartilages tend to get torn whenever there is any injury to the knee. The injury may be mild or moderate and may not even be noticed by the person at the time.
In your case, I believe that you have injured the meniscus in the outer side of the knee - the lateral meniscus. This is causing the pain when you bend your knee. There will be no pain when the knee is not bent much.
You will need to consult an orthopedist (a bone doctor) for an examination and treatment. Treatment usually consists of removal of the torn bits of cartilage.
You can read more about this here:
I hope this helps.
Your symptoms now confirms the diagnosis even more.
The menisci are cartilages that are present between the thigh bone and the lower large bone of the leg. So, pressure over the upper end of the large bone, ( just below the patella or the knee cap) will cause pain in case you have an injured menisci. The knee will not pain directly unless there is a major injury with inflammation.
A torn or injured menisci does not pain all the time. If the injury is slight, pain will occur only when pressure is applied to it directly or when the knee is bent in certain positions.
A torn meniscus may not necessarily cause pain when jogging. Pain can occur only when pressure is applied on the spot directly.
But the fact that you have a weakness of the leg is not consistent with a torn meniscus. It occurs only when there is pressure over the nerve supplying the muscles of that region. This compression can occur when the nerve curves over the bone called fibula just below the knee or it can occur if there is a tumor or growth in that region.
Please consult an orthopedic doctor - you will need an Xray plus MRI scans for an accurate diagnosis.