A lot of knee pain while in seated position or after sports..

Patellofemoral pain: Sports and seating with your knee bent can both increase load between your kneecap (patella) and the underlying femoral trochlear groove and accentuate underlying patellofemoral pain. The cartilage may be injured. Thorough examination of your knee is warranted by your physician or an orthopaedic surgeon to elucidate the underlying cause in your particular case. Xrays and an MRI may be indicated.

Kneecap: A common complaint of people with patellofemoral (kneecap) problems is pain after sitting in one position for awhile. It is often accompanied by pain in the front of the knee doing stairs or deep knee bends. Stretching the quads and hamstrings is helpful. Aleeve or Motrin helps the pain. A good exam and xray would shed light.