The aim of this study is to investigate the effect of upper limbs motion on lower limb biomechanics and muscle activity during single-leg jump landing after anterior cruciate ligament reconstruction.

More and more people join in different sports in recent years. But the incidence of sports injury also increases. And the most frequently occurring and debilitating knee injury in sports is rupture of the anterior cruciate ligament (ACL). Patients who aim to return to their preinjury sports should undergo anterior cruciate ligament reconstruction (ACLR) in order to maximize knee stability. The overall incidence rate of a second ACL injury within 24 months after ACLR was nearly 6 times greater than that in healthy participants. Although many studies have showed about biomechanical and neuromuscular risk factors during jump landing which were thought to associate with the secondary injury after ACLR, these studies all focused on the motion of lower extremity. But actually, people often use their upper limbs to catch or throw a ball during jump landing in playground. Whether the upper limbs motion will affect the muscle coordination of lower extremity during jump landing is still unknown. Therefore, the purpose of our study is to investigate the effect of upper limbs motion during single-leg jump landing after ACLR.

Inclusion Criteria:

• Only one leg has operation of ACL reconstruction
• At least 1 year after ACLR or have been back to sports
• Exercise in sports regularly.

Exclusion Criteria:

• Other operation of lower extremity exclude ACLR
• Any diseases or poor condition that will affect jumping or deterioration after jumping.

Age between 20-50 years old