Push
Knee push-ups are the modified variant that lets beginners build upper-body strength without supporting full body weight. They are useful when incline push-ups are still too hard.
Kneel with knees slightly behind the hips. Hands at shoulder width or slightly wider. Body forms a straight line from knees to head. Lower the chest until it touches or nearly touches the floor. Push back up. Hips must NOT rise into an inverted V; stay aligned throughout.
When you can do 3×15-20 with perfect alignment, start mixed sets: do what you can from the feet, then finish from the knees.
Advanced athletes can also use them for active recovery or as a chest warm-up.