Tag Archives: Anterior Cruciate Ligament

Knee Osteoarthritis and ACL Injury

ACLSix months (+/- a few) is the standard time needed for an athlete to return to competition following anterior cruciate ligament (ACL) surgery. To reach this date, therapy must be thorough and exact. Range of motion, neuromuscular control, or strength deficits that go unaddressed, negatively influence return to play and can also lead to other long-term consequences.

Those who suffer from ACL injuries are at greater risk of developing knee osteoarthritis (OA). Knee OA is a condition whereby the cartilage slowly wears away. This is a painful, life-long health issue that can lead to disability. With proper rehabilitation and adequate strengthening of the quadriceps, OA can be prevented. Sounds simple, but clinicians must also deal with arthrogenic muscle inhibition (AMI).

ASpinal tractMI is a neuromuscular dysfunction that limits the ability to strengthen muscle and is common following ACL surgery. With AMI, neurological signals from the quadriceps muscle to the brain and spinal cord are interrupted or slowed. You can read more about Brain and CNS deficits here.  So the question is, how do you combat AMI to properly strengthen the quad and subsequently prevent knee OA? The answer might be vibration training.

Vibration training employs a low-amplitude, low-frequency mechanical stimulation that exercises musculoskeletal structures. Vibration training provides strength gains without joint loading and stimulates osteoblastic and chondrocyte activity through the mechanisms of  Power Platemechanobiology. Subsequently, bone and joint health are improved.

A recent article by UNC’s EXSS Impact site found that vibration training (local or whole-body) improves quadriceps function by improving central nervous system function. Following vibration training, brain activity was altered in such a way that it became easier for these subjects to activate and use their quadriceps muscles. As such, muscle vibration can be an effective method to improve quadriceps strength and reduce the risk of developing knee OA.

Below is the full article from UNC.

Why did you do this study?

Individuals with anterior cruciate ligament (ACL) injuries are at greater risk of developing osteoarthritis (OA). OA is a considerable burden on the US healthcare system and contributes to physical disability and comorbidities such as obesity and diabetes. The lifetime cost of ACL injury amounts to $7.6 billion annually for patients that undergo reconstruction, $17.7 billion for patients that undergo non-surgical rehabilitation. Quadriceps dysfunction is ubiquitous following ACL injury and reconstruction, and is a major contributor to the development of OA. The quadriceps are responsible for absorbing impact forces during everyday tasks like walking and stair climbing, and also athletic tasks like running and jumping. When the quadriceps fail to act appropriately, their ability to attenuate these forces is reduced, and cartilage within the knee joint experiences greater loading. Subtle increases in joint loading are amplified through repetitive activities like walking, and over time, greater loading contributes to a gradual breakdown of articular cartilage.

Given the implication for future OA development, the restoration of proper quadriceps function is extremely important in rehabilitation. However, quadriceps dysfunction is caused by a neuromuscular phenomenon called arthrogenic muscle inhibition (AM), which presents a substantial limitation to muscle strengthening. Essentially, sensory signals from the knee joint inform the central nervous system – the brain and spinal cord – that the ACL as been injured. In response, our central nervous system responds by inhibiting the quadriceps to prevent further damage of the injured joint. While this mechanism may protect the joint in short term, AMI persists for many years following the initial injury and is thought to contribute to excessive cartilage loading and the development of OA. Therefore, strengthening the quadriceps is important in rehabilitation, but traditional exercises do not address AMI. Novel rehabilitation modalities are needed to combat AMI prior to the implementation of strengthening exercises.

Previous work in our laboratory indicates that muscle vibration provided directly (local muscle vibration – LMV) and indirectly (whole body vibration – WBV) may improve quadriceps function. However, what remains unclear is the mechanism by which these vibratory stimuli actually work to enhance muscle function. Given that AMI involves alterations in central nervous system function, it is imperative to understand how muscle vibration influences characteristics of spinal cord and brain function. Therefore, the purpose of this study was to understand how both WBV and LMV influence characteristics of central nervous system function.

What did you do and what did you find in this study?

Left - Transcranial magnetic stimulation to assess cortical neuron excitability; Right - Whole body vibration platform

We recruited subjects with ACL reconstruction for this study. First, we measured various characteristics of quadriceps function (i.e. strength and activation), and also how the brain and spinal cord contribute to muscle contraction. Following baseline measurements, subjects received an intervention of WBV, LMV, or control (no vibration) treatment. We repeated the same measurements of quadriceps function and central nervous system function following the treatment.

Active motor threshold was used to assess corticomotor excitability. In this case, both WBV and LMV lowered AMT relative to the control condition. This indicates that it becomes easier for the brain to activate the quadriceps following treatment. (* indicates P<0.0083)

We found that both WBV and LMV acutely improved quadriceps function (strength and activation) relative to the control treatment, and that this improvement was likely due to greater cortical neuron excitability. In other words, muscle contraction can either be voluntary (the brain tells the muscle to contract) or involuntary (spinal reflex loops). What we found was that following WBV and LMV, brain activity was altered in such a way that it became easier for these subjects to activate and use their quadriceps muscles.

How do these findings impact the public?

These findings indicate that vibratory stimuli acutely improve quadriceps function, and could be useful in addressing deficits in central nervous system function such as AMI. As such, muscle vibration could be an effective method to improve quadriceps strengthening protocols following ACL injury, and in turn reduce the risk of developing knee OA. Overall, knee OA is a major economic burden on the US healthcare system, and these findings could have important relevance for alleviating healthcare costs and physical disability.

A comprehensive rehabilitation program is vital for an athlete’s return to competitive sport. Failure to normalize range or motion, strength, and neuromuscular control can result in performance loss, reinjury, or long-term disabilities, such as knee OA. Make sure your rehabilitation program is inclusive of all components. Of course, the best cure for ACL surgery is preventing ACL tears all-together. If you want to prevent ACL injury, read about the RIDS Program designed to prevent injury. 

RIDS Program: A New Paradigm for ACL Prevention

ACLThe grandeur of the World Cup is upon us. The world’s most popular sport has its chance to shine. As soccer gets its much deserved pedestal, summer camps fill. High school and collegiate soccer athletes become inspired. Training begins and with that begins the season of the ACL. With approximately a quarter-million ACL injuries per year, it is safe to say the injury is common in sport. Though most common in female athletes, ACL injuries happen to anyone anywhere, with soccer, basketball, and gymnastics athletes being at most risk.

While an ACL injury is traumatic in nature, the injury is rarely due to direct trauma. More than 75% of ACL injuries are non-contact in nature (1). Non-contact ACL injuries stem from a complex interaction of anatomical, hormonal and neuromuscular factors. Recent studies suggest that ACL injuries are caused by both neuromuscular fatigue and unanticipated movements commonly found in athletics, such as evasive maneuvers that involve some form of deceleration, change of direction, or landing. The coupling of these movements with modifiable risk factors (see graphic) is what leads to non-contact ACL injury. The good news is that non-contact ACL injury can be prevented by addressing these modifiable risk factors. Continue reading

ACL Injury: New Information on Prevention, Rehabilitation, and Consequences

I have written about knee injuries so much. Every day we are bombarded with research that quite frankly, it gets boring. The problem is with approximately a quarter-million ACL injuries per year, it is safe to say the injury is rampant. The devastating nature and commonality of the injury has provided loads of information on prevention, rehabilitation and mechanisms of injury. I am not going to regurgitate them all, but do want to share some recently published articles that sports medicine experts should read.

Article 1: Negahban, Et al. A systematic review of postural control during single-leg stance in patients with untreated anterior cruciate ligament injury. Knee Surgery Sports Traumatology and Arthroscopy, May, 2013.

I love systematic lit reviews and this SLR aimed to determine postural control on those with ACL injuries. We have many internal systems and senses that help us balance.  Beyond the use of our eyes and ears to sense balance, tiny mechanoreceptors and proprioceptors exist in our tissue that sense abnormal movement. This study found that when the eyes are closed individuals with ACL injuries had increased postural sway and loss of balance. This indicates that the injury and inflammation following injury inhibits our body’s internal mechanism to sense balance. When rehabilitating, be sure to emphasize proprioception exercises.

Article 2: Thomas, Abbey, et al.  Lower Extremity Muscle Strength After Anterior Cruciate Ligament Injury and Reconstruction. Journal of Athletic Training published online first, 2013.

Despite advances in rehabilitation and the numerous studies published on ACL rehabilitation protocols, we appear to be failing. This study shows that at 6 months Status Post ACL reconstruction that global weakness still exists. When comparing strength output from injured vs. uninjured legs it appears the knee-extensors (quads) and knee flexors (hamstrings) are weaker at 6 months when compared to the contralateral side. Conversely hip and ankle strength was not significantly different at 6 months. The timeline to return a player back to competition and activity is 6 months following activity and/or 95% strength of the uninjured side. This study indicates 6 months might be too early. Also, we may need to adjust our strengthening protocols to further stress knee flexion / extension strength.

Article 3 – Bell, DR, Clark, MA, Padua, DA, et al., Two- and 3-Dimensional Knee Valgus Are Reduced After an Exercise Intervention in Young Adults With Demonstrable Valgus During Squatting. Journal of Athletic Training published online first, 2013.

Darin Padua and the UNC Department of Exercise and Sport Science has done a lot of work on knee displacement and correlating the findings with ankle hypomobility and hip underactivity. This particular model used the NASM Corrective Exercise Model as the intervention procedure. This method systematically turns off hyperactive tissue and activates hypotonic tissues. The data revealed that following intervention of the ankle and hip medial knee displacement was significantly reduced.  This information is important as several studies have shown medial knee displacement to be a primary cause of ACL injuries and chronic knee pain.

Article 4: Ericksen, et, al. Different Modes of Feedback and Peak Vertical Ground Reaction Force During Jump Landing: A Systematic Review. Journal of Athletic Training published online first, 2013.

The inability of the body to absorb and control joint movement during high levels of ground reaction forces has been shown to increase risk of ACL injury as well as other chronic knee conditions.  This study evaluated the effect of expert provided and self-analysis feedback reduced peak ground reaction forces. This is not a paramount study but does shows the effectiveness of verbal queuing and observation to correct suboptimal neuromuscular control, specifically during landing and absorption of ground reaction forces through the kinetic chain. Rehab practitioners should incorporate feedback to teach clients appropriate muscle control during ACL rehabilitation.

I would like to say thank you to Darin Padua, PhD, ATC for keeping me abreast with current data. Darin is a leader in sports medicine research and specifically has many published papers on ACL injuries. Darin manages his blog site and also shares info on his twitter account. If you are a health and wellness professional seeking important information rehabilitation and prevention of injury, I recommend you give Darin a follow.

Cheers!