Many sports, such as soccer, basketball and football involve jumping, cutting and pivoting maneuvers. These motions place stress and demands on the ligaments that support the knee. One of the most common injured ligaments is the anterior cruciate ligament(ACL).
ACL injuries continue to be one of the most common injuries in sports today with an estimated of over 200,000 injuries occurring annually according to the American Academy of Orthopedic Surgeons(AAOS) at a cost of approximately $17,000 per ACL injury. The focus of this article is to review the common causes of ACL injuries, difference between common ACL surgeries; post-surgical rehabilitation, and evidenced-based post-therapy recommendations.
Risk Factors/Mechanism of Injury
The ACL prevents anterior translation of the tibia relative to the femur. The anterior cruciate ligament is injured when the tibia(lower leg bone) is struck while extended pushing back on the femur(upper leg bone). Typically the athlete will hear a “pop” and sustain immediate local pain with the inability to bear weight and extend the knee. The risk factors that have been previously studied contributing to ACL injuries for non-contact ACL injuries fall into four distinct categories: environmental, anatomic, hormonal, and biomechanical.4 Anatomically, women possessing a wider Q-angle then men which places a greater valgus stress to the knee. During a women’s menstrual period, research has shown there is increased joint laxity within the knee. Biomechanically, according to the research by Jacobs et al, women form landing from a jump demonstrated increased valgus potentially increasing the risk for injury. Furthermore, correlations between hip abductor strength and landing kinematics were generally larger for women than men, suggesting that hip abductor strength may play an important role in neuromuscular control of the knee.6
ACL Surgical Intervention
Surgeon experience and preference, graft availability and tolerance to harvest the morbidity determine which graft will be used.3 Listed below are two of the common surgeries for ACL reconstruction; patellar tendon and hamstring graft. The patellar tendon procedure is listed below as seen in Figure 1. Patellar Tendon Reconstruction
|Figure 1. Pattelar Tendon Reconstruction||Figure 2. Exposure following graft harvest is made to prepare the bone graft.|
|Figure 3. The graft is then taken and prepared.||Figure 4. Hamstring graft procedure|
Sutures are pulled through and the graft is advanced into the femoral tunnel until the mark on the graft is visualized at the entrance of the femoral tunnel. The incision and portals are closed in layers and steristrips and a temporary dressing is applied.
The goal of physical therapy is to first restore mobility and then promote stability. Rehab is typically divided into four stages of four weeks each. Between 12-14 weeks post-surgery, jogging is introduced and continued proprioceptive exercises to prepare for higher-level training. At 16 weeks post-surgery both running and plyometrics are instructed to the athlete to assist with regaining speed, quickness, and power.
Once discharged from physical therapy, the goal is continued strengthening of hamstrings and hip extensors to continue to reduce stress to the anterior knee. Since the quadriceps are dominant and biomechanically stronger according to the research. Implementation of core strengthening, multi-directional strengthening, cross training such as swimming and hiking is fundamental.
Many studies have shown that women are more likely to have ACL injuries than men, Landry et al asked 42 elite adolescent soccer players to perform an unanticipated side-cut maneuver while 3D kinematic, kinetic and electromyographic lower limb data was collected. Females demonstrated greater rectus femoris activity throughout stance and demonstrated les hip flexion during the side-cut test. The researchers concluded that the muscle imbalance activity and reduced hip flexion may all have contributing roles in the higher noncontact ACL injury rates.1
Hewett et al wanted to examine if neuromuscular training can reduce the incidence of knee injuries. Through his study, he found three neuromuscular imbalances encountered in female athletes. One imbalance is the tendency for the female athlete to be “ligament dominant.” A classic clinical example is the box jump test. Here the athlete is asked to jump off a box. When landing, they demonstrate a valgus knee deformity indicating decreased neuromuscular control and anatomically due to a weaker glute medius. They reported that female athletes allow stress on ligaments to absorb ground reaction forces before muscle activation. Another imbalance is termed “quadriceps imbalance.”With quadriceps dominance, the knee extensors are activated preferentially over the knee flexors to stabilize the knee joints. The final imbalance is “leg dominance.”
Leg dominance is the imbalance of muscular strength and coordination between opposite limbs.2 Their electromyographic studies further documented quadriceps dominance and muscular imbalances in the coronal plane. The study showed that female athletes activate quadriceps in an unbalanced manner, compared to male athletes.2
Return to Play
Scientific evidence combined with experienced-based empirical evidence has created a new training approach for neuromuscular training. The three essential training components of neuromuscular training are dynamic, biomechanically correcting movement patterns, neuromuscular patterning to correct the neuromuscular imbalances and constant biomechanical analysis both during and after training.5 Returning to sport is contingent on several factors. The average athlete returns to playing sport between 6-9 months post surgery. The decision to return to competition is individualized and is often based on the input from the “team” including the athlete themselves, physicians and physical therapists. Athletes must demonstrate pain-free range of motion, posses strength of 85% or greater as compared to the uninvolved leg and pass functional limb testing.
Female athletes may demonstrate one or more neuromuscular imbalances of ligament dominance, quadriceps dominance and leg dominance. Correction of neuromuscular imbalances is important for optimal movement for the athlete and reduction in knee injuries. By understanding the role the anterior cruciate ligament plays, the biomechanics it serves with dynamic movement, preventive strategies discussed, the personal trainer has the knowledge to be able to work with a client who has gone through ACL reconstruction.
1. Roninger, Lori Rochelle. Lower limb gender differences in athletes linked to ACL injuries. Biomechanics. February 2008. Page 11.
2. Hewett, Timothy, Myer, Greg., Ford, Kevin. Dynamic balance: Can neuromuscular training prevent ACL injuries? Biomechanics. Pages: 22-32.
3. Starkey Chad, Johnson, Glen. Athletic Training and Sports Medicine. 4th edition. Jones and Bartlett. Sudbury, Massachusetts. 2006. Pages: 138-142.
4. Letha Y. Griffin , et al. Noncontact Anterior Cruciate Ligament Injuries: Risk Factors and Prevention Strategies. Journal of American Academy Orthopedic Surgeons. Vol 8, No 3, May/June 2000. Pages: 141-150.
5. Myer, Gregory., Ford, Kevin., Hewitt, Timothy. Rationale and Clinical Techniques for Anterior Cruciate Ligament Injury Prevention Among Female Athletes. Journal of Athletic Training. 2004 Vol 39(4). Pages: 352-364.
6. Jacobs, Cale A., Uhl, Timothy., Mattacola, Carl G., Shapiro, Roberto., Rayens, William. Hip abductor function and lower extremity landing kinematics: sex differences. Journal of Athletic Training. 2007. Vol. 42(1). Pages: 76-83.
Chris Gellert, PT, MPT, CSCS, CPT is the President of Pinnacle Training & Consulting Systems. Gellert offers educational workshops on human movement, home study courses on human movement, and consulting services. As a clinician, author, presenter, he has over 19 years experience having treated and worked with individuals of all ages with various spinal injuries, post surgical conditions, traumatic and sport specific injuries in industrial rehabilitation, outpatient and private practice settings. For more information, contact www.pinnacle-tcs.com or call 443-528-0527/(888)586-4188.