Preventing Knee Injuries
By: Nicole Ettorre CAT(C), BAHSc (AT), BPhEd
Whether you are a weekend warrior or a highly competitive athlete, you have likely experienced or come in contact with someone who has suffered from some sort of knee pain. Knee injuries, especially to those who are physically active, have become increasingly prevalent and are responsible for large
economic and personal burden 1
The knee itself is a large and complex joint that can be easily injured due to the number of forces that can act upon it. It consists of four bones: the femur, tibia, fibula and patella; cartilage, meniscus, and several bursa, ligaments and muscles/tendons. All of these structures must work together to produce movement and provide stability to prevent injury.
Knee Injury
Anterior knee pain is the most common knee disorder, affecting 1 in every 4 active individuals. It accounts for 25-40% of all knee problems presenting to sports medicine clinics 1 . Women are 6-8 times more predisposed to knee injuries than male counterparts in sports that require jumping, landing, cutting, and pivoting maneuvers 3 . Anterior cruciate ligament injuries are one of most disabling injuries of the knee joint resulting in long term neuromuscular deficiencies. Of those who have sustained an ACL injury, approximately 70% will not return to sporting activities 3 . Non-contact ACL injuries account for about 80% of all ACL injuries, with 70% occurring during ground contact after landingfrom jump and the other 30% occurring while decelerating to change direction 3 . According to a meta-analysis performed by
Ratzlaff and Liang (2010); examining the relative effectiveness of six interventions for reducing ACL injuries in females; they found that neuromuscular training may reduce ACL injuries if plyometrics,

balance and strengthening exercises are incorporated. However, training sessions must occur more than once per week and are a minimum of 6 weeks in length 5 .
The mechanisms of both patellofemoral pain syndrome and ACL pathology include anatomic and biomechanical factors such as knee valgus, weak hips and core, patellar malalignment, increased femoral internal rotation and ankle and foot malalignments 3 . Repetitive activities performed with biomechanical malalignments predispose soft tissue around the knee joint to increased pressure that leads to the inflammation and pain experienced in patellofemoral pain styndrome 3 .
There is a high risk of knee osteoarthritis from knee joint injury. Approximately 50% of individuals with an ACL or meniscus tear will develop knee OA 5 . According to a review by Ratzlaff and Liang (2010); in male and female soccer players sustaining ACL tears, approximately 80% had radiographic OA 12-
14years later. Of those reported having OA, 70% had functional limitations and reduced quality of life due to their knee 5 . The high incidence of knee OA aftr injury is a strong rationale to direct increased efforts toward prevention of knee injury and improved knee injury management 5 .
Risk Factors
Risk factors for knee injury can be either intrinsic (anatomic, neuromuscular, hormonal) or extrinsic
(environmental, including knee bracing, shoe-surface interface, weather) 5 . Other factors associated with
ACL injury include less knee flexion, decreased core and trunk control and increased hip flexion, and landing flat-footed and with less plantar flexion 5 . Research has also shown that poor muscle flexibility and neuromotor control are predisposing factors for the development of anterior knee pain 1 . In particular, the quadriceps play a key role in the cause of anterior knee pain due to imbalances between vastus medialis oblique and vastus lateralis which could cause lateral patellar tracking and subluxation.
Ratzlaff and Liang (2010) have stated that studies of neuromuscular and biomechanical substrate of knee injuries show that most knee injuries are not the result of contact or collision. Distinctive biomechanical patterns, such as excessive coronal plane motion (valgus collapse), are seen when the knee is injured 5 .
Knee Injury Prevention
By now you must be thinking “I’m doomed!” It seems like it right? But have no fear, research shows that moderate physical activity and specific exercise regimens play a significant role in prevention of knee
OA 5 . Herman et al. (2012) highlights the importance of musculoskeletal injury prevention, as it is estimated that 22 million sports injuries occur in the UK each year 2 . Preventative exercise programs may lead to fewer injuries and training hours lost in athletic groups and lower medical costs among the general population 1 . A study by Coppack et al (2011) investigated the effects of exercise for the prevention of overuse anterior knee pain in young military recruits. There were 1502 participants that underwent a 14 week military training program. The intervention group completed a prevention training program consisting of: isometric hip abduction against the wall in standing, forward lunges, single-leg step downs from 20cm step, single-leg squats to 45 degrees with isometric gluteal contraction, and stretches of the quadriceps, ITB, hamstrings, gastrocnemius. The control group followed existing training syllabus warm-up exercises. The results of the study indicate that a simple set of lower limb stretching

and strengthening exercises can result in a substantial and safe reduction in anterior knee pain 1 . An MRI study of children aged 9-18 years found that younger children, males and those undertaking more vigorous sports have substantially higher articular cartilage accrual rates. This evidence supports the prescription of vigorous physical activity for optimum joint development in children, which would also reduce childhood and possibly adult obesity 5 . Thus, injury prevention programs should target school and university aged students through physical education curriculums and improved sports associations 5 .
Adolescent ACL injury prevention programs should incorporate a supervised preseason and in-season dynamic warm-up, stretching exercises, lower extremity strengthening exercises, plyometrics, balance, and sport-specific agility. Paszkewicz (2012) states that emphasis should be placed on proper landing technique stressing a “soft landing” and deep hip and knee flexion 4 . Studies have shown reductions in lower extremity injury rates using training protocols that focus on landing mechanics, balance training, strength training, and/or agility training 4 . Close kinetic chain functional strengthening exercises have been shown to increase VMO and VL activation patterns and improve patellofemoral joint alignment in healthy adults 1 . Other muscles that should be targeted in an injury prevention program include gluteus maximus, gluteus medius, quadratus lumborum, multifidi, transversus abdominis, and hamstrings 3 .
Stretching of soft tissue structures has been proven to reduce pain and increase flexibility in patients with anterior knee pain 1 . Neuromuscular training programmes are thought to improve joint position sense, enhance joint stability and develop protective joint reflexes, ultimately preventing lower limb injuries 2 . Neuromuscular training, landing instructions, and custom orthotics are among most evidencebased intervetions proven to decrease biomechanical impairments that lead to knee injury 3 .
Functional Screening
Assessment of dynamic stability through functionional tasks is an easy and effective way to implement an injury preveniton strategy. Functional tasks help assess and identify a variety of biomechanical deficiencies, especially in closed kinetic chain activities that cause knee injuries 3 . Listed below are three simple tasks that will give you a lot of information regarding biomechanical deficiencies:

Squat (Bilateral and single-leg)

Step Down

Drop Jump

Flexibility o Glutes, Hamstrings, Quadriceps, ITB, Gastroc-Soleus, Hip Flexors

Strength (Quadriceps, Gluteals, Hamstrings, Core)

o Stiff-legged Deadlifts, Lunges, Squats, Monster Walks o Russian Twist, Ab Rollout, Woodchoppers

Plyometrics o Backward/forward/lateral jumps, box jumps, bounding, depth jumps, lateral box push offs

Balance/Proprioception o Cariocas, Wobble board balancing

Agility o Rope skipping, Agility T Drill, Sprint Lateral Shuffle, Illionois Course
To maximize the benefits of an injury prevention program, incorporate yoga and pilates into your exercise regime. When practiced regularly, the benefits are numerous. Physically, a combination of yoga and pilates can improve muscular strength, endurance, flexibility, postural alignment, body awareness, circulation, digestion, hormonal balance, respiration, immune function, strengthen bones, normalize blood pressure and reduce or normalize body weight. Mentally, it can improve your alertness, concentration, sleep patterns; reduce stress and anxiety and improve your ability to relax. The key benefit is an overall state of health and wellbeing.
References:
1.
Coppack, R., Etherington, J., and Wills, A. (2011). The Effects of Exercise for the Preventionof
Overuse Anterior Knee Pain. The American Journal of Sports Medicine. Vol 39, No. 5. 940-948.
2.
Herman, K., Barton, C., Malliaras, P., and Morrissey, D. (2012). The effectiveness of neuromuscular warm-up strategies that require no additional equipment, for preventinglower limb injuries during sports participation: a systematic review. BMC Medicine. 10:75. http://www.biomedcentral.com/1741-7015/10/75
3.
Ortiz, A., and Micheo, W. (2011). Biomechanical Evaluation of the Athlete’s Knee: From Basic
Science to Clinical Application. American Academy of Physical Medicine and Rehabilitation. Vol
3, 365-371. Apr 2011
4.
Paszkewicz, J., Webb, T., Waters, B., McCarty, C., and Lunen, B. (2012). The Effectiveness of
Injury-Prevention Programs in Reducing the Incidence of Anterior Cruciate Ligament Sprains in
Adolescent Athletes. Journal of Sport Rehaiblitation. 21: 371-377.
5.
Ratzlaff, C., and Liang, M. (2010). Prevention of injury-related knee osteoarthritis: opportunities for the primary and secondary prevention of knee osteoarthritis. Arthritis Research & Therapy.
12:215. http://arthritis-research.com/content/12/4/215