ACL Non-Contact Injuries Part II (by guest contributor Anna Napolitano)


Much emphasis has been placed on proper landing techniques for female volleyball and basketball athletes.  Body position and alignment during jump landings along with proper joint angles and range of motion are important factors to investigate.  Studies have found that NCACL injury possibly occurs in all three planes of motion due to increased knee internal rotation, increased knee valgus and decreased knee flexion during jump landings (Laughlin et al, 2011).  Valgus collapse (knee valgus) may result due to poor timing of the activation of the gluteus medius.  Valgus collapse is also associated with increased ankle pronation and subtalar joint eversion especially during a jump landing.  Decreased knee flexion (most often seen with decreased hip flexion) leads to increased anterior shear forces or increased anterior translation of the tibia over the femur.  With minimal hip and knee flexion occurring, a greater force of the quadriceps occurs to absorb the momentum of the jump landing therefore pulling the tibia forward over the femur.  If the hamstrings are unable to counter this force, then a NCACL injury may occur.  Joseph et al. found increased frontal plane motion during a drop jump test occurring more in females than males and found female athletes exhibiting greater valgus angular velocity (2011).  Increased angular velocity generally occurs during sport specific drills forcing female athletes to adapt to ever changing environments at a quick pace.

Most studies have investigated basketball or volleyball landings separately.  Few studies have compared jump landings between the two sports at one time.  Lee Herrington (2011) investigated knee valgus angles during jump landings between volleyball and basketball athletes.  The results could help identify possible sport specific situations that would place females at greater NCACL risk.  The Herrrington study found no difference between single and bilateral jumping tasks in volleyball athletes (2011).  Basketball athletes showed a decrease in knee valgus angle during the unilateral jump tasks (2011).  A decrease in knee valgus shows greater dynamic hip and knee joint stability and strength.  During the unilateral jumping task volleyball athletes exhibited greater knee valgus than basketball athletes for both the left and right knees (2011).  In contrast the female basketball athletes displayed greater knee valgus angle control during the unilateral task (2011).  The differences here could be related to sport specific skills and demands found unique to that sport.  During volleyball, especially at the middle blocker position, knee, hip and ankle joints are placed at greater risk as the blocker moves across the net to defend the opposing attackers.  Often times when blockers move to the outside or right side of the net to block, their ensuing footwork requires the athlete to maintain stabilization and move quickly to their necessary target.  If there are any imbalances within the lower extremity muscle chain then the forces experienced by the athlete as they move across the net places he/she at possible higher risk of NCACL injury.

Kinematic asymmetries, although not desired, are common among athletes.  Single limb dominance is a common theme however strong research to support it does not exist.  Females could present with greater kinematic asymmetries than males when performing jump landing tasks explaining their “dominance” in NCACL injuries.  During forward jump landings, females displayed greater asymmetry than males in knee valgus and ankle abduction (Pappas and Carpes, 2011).  Ankle abduction increases stress along the medial aspect of the knee joint therefore possibly increasing the amount of knee valgus measured.  Also, the asymmetry presented could have been right limb vs. left limb dominance during landings.  Navicular drop and subtalar pronation are associated with ankle abduction (Pappas and Carpes, 2011).  Females displayed greater asymmetries than males with ankle joint kinematics in the frontal plane as well (Pappas and Carpes, 2011).  Ankle motion in the frontal plane is necessary for shock absorption.  Increased ankle movement leads to internal rotation of the tibia and preloading of the ACL (Pappas and Carpes, 2011).  If the ankle is unable to absorb the extra movements and forces the lower extremity experiences during jump landings, more stress will be placed on the knee and hip joints placing the ACL at greater risk for injury.


Just Back from the Salt Lake City Functional Foot Course!

Great job everyone at this past weekend’s Functional Foot course in SLC! Dan and I enjoyed sharing with you all and look forward to sharing more on!
Keep learning and growing! The Functional Foot course will go to Phoenix next on April 27 & 28. Take care! Have a blessed Easter!


Welcome to The Functional Foot Blog!

From Dan:
Welcome to The Functional Foot. Chad and I are very excited about our new course and the opportunity to share and learn from all of you. For this first “blog” we would like to give a shout out to those who have inspired us in developing The Functional Foot. A huge thank you to Gary Gray and the Gray Institute ( As a pioneer in the notion of “functional thinking” Gary inspired Chad and I to ask basic questions about movement and consider the myriad of dynamic contributions of the foot to the entire lower extremity. Gary developed what we believe to be the first functional foot seminar “When the foot hits the ground everything changes” back in the late 1980’s. Even at that time, Gary’s footprint left an indelible mark on our path to functional thinking. I am personally indebted to Gary as he took me under his wing when I was a newly developing clinician – gently nudging me to think more practically and to truly appreciate the role of common sense in clinical decision making. I would also like to thank Don Neumann ( for helping me to better understand the function at the hip. Don, like Gary, is an amazing and visual teacher, and his lectures on hip muscle and hip joint function are a must see by every orthopaedic rehabilitation specialist. So, between Gary and Don, I almost understand the relationship between foot function and hip function, with the knee being caught in the middle.

From Chad:
I also welcome you to The Functional Foot! Like Dan, I am thrilled to be a part of this new concept in on-going professional education and development. Our hope is that the participants of The Functional Foot courses will join our network of professionals in continual “on-line” learning opportunities with our “Blog” and “Forum” areas of the website. We look forward to collaborating with you in order to develop your skills, problem solve, inspire, and encourage one another in our practices. We hope that these opportunities will help you (our participants) retain what you learn at our course(s) and be able to more effectively implement your skills with patients in a day-to-day real life world. We would be remiss if we did not recognize our families for their support of this endeavor! Melissa and Jackie, thank you for your help, support, and tireless patience with Dan and I taking pictures of your feet!

From Chad and Dan:
The main point of “The Functional Foot” is to create a collaboration between practicing clinicians (PT’s, PTA’s, AT’s, OT’s, etc.), educators, and other individuals involved in health and wellness promotion for the essential purpose of making us all better at what we do – that of helping our patients and clients. The Functional Foot, as an attendance based seminar, provides hands-on training for examination of and intervention for the lower extremity, with a focus on the foot. The Functional Foot, as a Discussion Board resource, provides an opportunity for participants to interact in discussions relative to treatment ideas, new examination approaches, findings in the research literature, and enhancing an “evidence-based” approach to clinical decision making. And the Functional Foot, as a “blog”, is an opportunity for individuals to contribute insights and challenges to all members – yes, you will be invited to blog with us…and have fun sharing. Our blogs will primarily consist of clinical practice observations, techniques, new ways to manage complex lower extremity problems, and information on new tools to help you and your patients in the clinic. We will also discuss the use of current research to assist us with decision making, beginning with articles on how to efficiently read a research article, critique it for its methods, without getting all hung up on those messy statistics. Chad and I believe that readers place too much emphasis on the “stats” and not enough on the “where did the data actually come from and can I value that data?”

Chad and Dan