Articular Cartilage Damage or Osteoarthritis or Osteochondritis dissecans

This is probably a reflection of the pain experienced during the movement and is present in both curves at the same point in ROM because the articular surfaces are involved. 

The torque curve deviation will be almost repeated throughout the repetitions.

This is seen more recently in articular cartilage damage. It often remains following chondroplasty or micro fracture demonstrating the surgery has not significantly affected the mechanics of the knee.