Pain in my knee cap after playing basketball, pain has lessened.i think it's a knee sprain. how long should i rest my knee until it fully recovers ?

Seven – 10 days: It sounds like patella tendinitis, especially if associated with basketball. Rest, ice, anti-inflammatory medication, quad stretching and quad strengthening are all helpful. Also, consider playing with a patellar strap. This offloads the force seen by the patella tendon with jumping on hard surfaces – basketball, racquetball, handball, tennis etc. Give time to get well. Sensible activities.