Internal Forces 2: Screening and Prevention of ACL injruies.

Question 1

What is the main role of the ACL?

Answer 1

Stabilises the knee through different translations.

Prevents anterior translation of the tibia.

Question 2

What is the Q-angle?

Answer 2

Line drawn from the second ASIS to central patella and a second line drawn from central patella to tibial tubericle. An increased Q-angle is a risk factor for patellar subluxation.

Question 3

What did Wang, 2010 report about the lower extremity biomechanics of single and double leg stop jump tasks?

Answer 3

• Peak knee extension moment and Peak knee valgus moment during landing is hgiher during single leg.
• Peak knee proximal tibia lateral and anterior shear force during landing is higher during single leg stop jump.

Question 4

What did Clarke, 2015 report about the dynamic knee joint mechanics after ACL reconstruction?

Answer 4

• Patients with ACLr elicit greater knee abuduction during cutting stance phase.
• ACLr displayed greater maximum knee flexion during the first 40ms of landing.

Question 5

What are the mechanical variables of a drop jump?

Answer 5

• Impact loading rate 10-90%
• Peak impact force
• Average Impact force
• Peak propulsive force

Question 6

What did McDonagh & Duncan, 2002 report about the interaction of pre-programmed control and natural strecth reflexes in human landing?

Answer 6

False floor at 85 and 50ms prior to actual ground contact = double the amplitude of EMG activitiy in: Gastrocnemius, biceps femoris and rectus femoris also increased.

Question 7

What happens with joint contributions as drop height reduces?

Answer 7

Reduction in contribution at hip and increase from the ankle during the energy absorption phase.

Question 8

What did Cressey et. al, 2007 report about unstable resistance training?

Answer 8

10 Weeks of lower body UST improved short and long lasting SSC jumping performance and 40-yard sprint.
UST compromises the eccentric preloading resulting in subsequent force production.

Question 9

Summary of Internal forces - ACL.

Answer 9

• High internal & knee abduction torques are belived to result in ACL injuries
• Drop jumps & single legged hop are valid indicators of potential risks
• Hip & knee flexion - extension & abduction - adduction strength training are a ll required to reduce the risk of injury
• UST requires more robust design and investigation of the subsequent effects when instability stimulus is removed.