Patella
The joint formed between the undersurface of your kneecap, or patella, and your femur is called the patellofemoral joint. Your kneecap is a triangular shaped bone embedded within the tendon of your front thigh muscles, the quadriceps muscles (so named because it is made up of four muscles). It acts as a pivot, in fact, it is the largest “pivot” bone in your body, increasing the power of your quadriceps by about 30%. The greatest force, and therefore the greatest source of wear and tear, acting on your kneecap is from your quadriceps.