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舊 2010-04-29, 13:48   #16
ozman
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Having read the articles on the cause of ACL injury, it appears that "rearward twisting fall" is the type of fall that predominantly threatens your ACL (see the video in posting #10)

In a rearward twisting fall situation, your weight is on your heels throughout the entire fall. That is where the trouble is - the heel. It takes very little force to bust your ACL.
If we can avoid falling rearward or keep the skis together during falling....does this help to reduce the injury of ACL??
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舊 2010-04-29, 19:27   #17
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作者: ozman 查看文章
If we can avoid falling rearward or keep the skis together during falling....does this help to reduce the injury of ACL??
Movements of the knee that place a great strain on the ACL can cause damage to the ligament in the following situation:
•Hyperextension of the knee, ie. if the knee is straightened more than 10 degrees beyond its normal fully straightened position, is a very common cause of an ACL tear. This position of the knee forces the lower leg excessively forward in relation to the upper leg.
•Pivoting injuries of the knee with excessive inward turning of the lower leg can also damage the ACL.

Often those are non-contact activities with the mechanism of injury usually involving:
•Planting and cutting - the foot is positioned firmly on the ground followed by the leg (and body for that matter) turning one direction or the other. Example: Football or baseball player making a fast cut and changing direction.
•Straight-knee landing - results when the foot strikes the ground with the knee straight. Example: Basketball player coming down after a jump shot or the gymnast landing on a dismount.
•One-step-stop landing with the knee hyperextended - results when the leg abruptly stops while in an over-straightened position. Example: Baseball player sliding into a base with the knee hyperextended with additional force upon hyperextension.
•Pivoting and sudden deceleration resulting from a combination of rapid slowing down and a plant and twist of the foot placing extreme rotation at the knee. Example: Football or soccer player quickly slowing down followed by a quick turn in direction.

Unfortunately, it appears that the only way to avoid ACL injury is if you stop skiing, volleyball, basketball, soccer and baseball.
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舊 2010-12-14, 13:23   #18
Mike
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Hope this gives a better understanding:
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舊 2011-05-29, 11:15   #19
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According to a recent study by the Norwegian, when a racer tears an anterior cruciate ligament (ACL) in the knee, the ligament is torn while the skier is still skiing, and then they crash.
A panel of sports medicine and skiing experts picked apart videos of 20 World Cup skiers who had suffered an ACL tear. It showed that when a skier is trying to make a turn on the course, but leaning too far backwards and inwards into the turn while off-balance, it causes the outer ski to lift off the snow. When the skier tries to reach out with his/her leg to get the ski back on the ground, the very back of the ski hits the snow, pulling the leg with it and rotating the lower leg. The force on the knee caused by this rotation is too much for the ACL.

http://ibnlive.in.com/generalnewsfee...es/703020.html
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舊 2012-07-06, 16:56   #20
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Post ACL injury care

If one is unfortunate enough to have an accident involving ACL, the most important aspect of post injury care is the RICE regime: Rest, Ice, Compression, Elevation.

You may or may not need crutches or a supporting brace, depending on the degree of pain you experience from the tear. Most doctors will encourage you to bare weight as tolerated (i.e. walk on it unless it hurts too much) after an ACL injury.

Ice the knee regularly for as long as swelling and pain persist.

While the joint is swollen, you should keep it elevated above the level of your heart. This encourages fluid to drain out of the knee, which will decrease swelling. In addition, perform ankle pumps; pointing toes up and down. A tensor bandage can be used to gently compress the joint, which also helps to reduce swelling.

Your doctor should also recommend some exercises that you can do to keep the joint mobile without stressing the injured knee. This should include quad contractions to help keep your quad muscles firing, and gentle range of motion exercises like heel slides. Avoid activities that cause pain, or stress the injured joint.

Regaining flexion and extension is very important after an ACL injury. If you have swelling and pain in the joint you may find that regaining flexion takes some time, and you probably won't be able to bend the leg normally until all the swelling has gone. Regaining extension is the priority, as full extension is required to walk normally.

ACL injury is often accompanied by deep bone edema (bruising). This can be seen in the MRI scan above as the darker staining on the bones. This can be a source of soreness and discomfort, but usually resolves (albeit slowly - it can take six months or more) over time.

Do you need surgery?
Deciding whether or not to opt for surgery is not easy. ACL reconstruction is a common surgery with a good outcome; the estimated success rate is 85-90%. However like any surgery it is initially painful and restrictive, and does require the patient to commit to a lengthy and demanding rehabilitation that can take between 6 months and a year, depending on the graft type used to form the new ligament.

The correct answer to this question will be very dependent on your personal situation, and you should always consult with surgeons before making a final decision. Your family doctor, a physiotherapist and an orthopedic surgery. Recovery from injury varies tremendously from person to person, and some people are able to live without an ACL without any restrictions on activity. However, surgery is generally recommended for anyone who wants to continue participating in high level sports such as skiing.

In general, the more active the patient the more strongly recommended it is that they seek reconstruction. Reconstruction is usually considered essential for professional athletes, and encouraged for anyone who has an active job or for whom sports are an important hobby. Ultimately the decision to opt for or against surgery is a very personal one, but the most significant factors to consider are:
1/. The level of instability in the knee
2/. The patient’s desire to return to sports or other activities
3/. The risk of further damage or joint deterioration in the future

If you opt for surgery, the optimal time frame is generally considered to be approximately six weeks after injury. Although some surgeons will operate right away, most require you to go through a "prehab" program to ensure that all swelling is gone and you have regained full range of motion in the knee (ROM) before operating. A patient going into surgery without full ROM will find it very hard to regain normal ROM afterwards.
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舊 2012-07-06, 17:06   #21
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ACL reconstruction

ACL Reconstruction (ACLr)
During an ACL reconstruction the remains of the original ACL are removed, and a graft is placed through tunnels that have been drilled through the tibia (shinbone) and femur (thighbone). The graft is then fixed in place with endobuttons (a small, button-shaped device that is wider than the tunnel and sits at the end of it), bioabsorbable interference screws (these gradually integrate with the new bone growth in the tunnel over time) and/or staples.

When the new graft is placed in the knee, it initially undergoes a period where cells die off and it becomes progressively weaker. It then gradually develops its own blood supply, and eventually lays down collagen and begins to resemble a true ligament. While the graft is revascularizing, it is very vulnerable to damage and stretching and so the early stages of rehab focus on regaining joint mobility while protecting the healing graft. As the graft strengthens and new bone growth fills the tunnels, more advanced exercises are introduced.

The exact duration of an ACLr rehab is dependent on both the choice of graft, and the individual surgeon. Commitment to rehab on the patient's part is a vital component of the success of an ACLr.

Graft choice
One of the biggest decisions facing a patient who has opted for ACL surgery is the kind of graft to use. There are three options, each of which has slightly different implications for fixation and healing time.

Autografts:
The most commonly used type of graft is the autograft. This is a graft made from the patient’s own tissue. The most common types of graft are taken from either the hamstring tendons (back of the leg) or patellar tendon (front of the knee, just below the kneecap). Autografts are preferred by many surgeons because the patient’s body is inclined to accept its own tissue well, there is no disease risk associated with the graft, and the healing process is faster.

Patellar tendon graft
A patellar tendon graft (also known as PTBP - patellar tendon bone plug) is taken from the middle third of the tendon, with bone plugs on either end removed from the tibia (shinbone) and the patellar (kneecap). These bone plugs give the patellar tendon graft its greatest advantage, which is that bone-on-bone healing inside the tunnels is both stronger and faster than other forms of fixation. The tendon forms a very strong graft that closely resembles the natural ACL. With a patellar tendon graft, the patient can normally expect to return to full activity in approximately 6 months.

The main disadvantage of this graft method is that is disrupts the normal function of the patellar tendon, leaving patients prone to tendinitis and anterior knee pain. Many patients have difficulty kneeling without pain following a patellar tendon autograft, and a small number report permanent discomfort when kneeling. It may not be a good choice for patients with existing patellar problems such as maltracking.

Hamstring graft
With the hamstring graft, two of the hamstring tendons are used: the semitendinosis and gracilis. These are folded over and stitched together to form a four-string graft. The graft has no natural bone plugs, and is usually fixed in place with either bioabsorbable screws inside the joint, endobuttons at the ends of the bone tunnels, and sometimes a staple for additional security.

Because the hamstring graft has no bone plugs, the bone tunnels have to completely fill in before the fixation is considered secure and consequently some activities are restricted for longer than with a patellar graft. However the donor site is easier to heal, with many patients reporting minimal long-term effect on hamstring strength and function. Patients can generally expect to return to full activity in approximately 7-9 months.

Quad tendon graft
A more recent development is the use of the quadriceps tendon for the graft. This has one bone plug for stronger fixation, and reduces the donor site problems that often result from a patellar tendon graft. This is still a relatively unusual technique compared to patellar tendon or hamstring.

Allografts: donor tissue
Allografts are donor tissue recovered from a cadaver; most often the patellar or achilles tendon. Allografts have the very significant advantage that they do not require harvesting of a patient’s body part, and hence have no healing requirement or complications for the donor site. However, the process used to sterilize and store the tissue results in the death of some of the graft’s original cells, and consequently a longer period is required for it to establish a blood supply and heal fully.

In addition to the longer healing process allografts carry a very small risk of disease from contaminated donor tissue, although this is minimal with modern sterilization techniques. Allograft patients can expect to return to full activity in 9-12 months.

Synthetic ligaments: LARS
LARS ligaments are the current generation of synthetic knee ligaments, made from industrial strength polyester fibres. These are gaining popularity as an alternative to auto- and allografts, but remain a relatively recent development as an option for ACL reconstruction. Earlier generations of synthetic ligaments were prone to failure in the longer term, leading to complications for many patients.

LARS ligaments can be used on their own or as a scaffold for an autograft. Generally a LARS ligament requires the stump of the torn ACL to be in place, and ceases to be a viable option for older injuries.

The biggest advantage of LARS ligaments is that they enable a much faster return to activity than a tissue graft. Many LARS patients are able to return to sports between 3 and 6 months following surgery. Post-operative pain is also reduced because no harvest site is required, and there is no risk of disease. Short-range data (up to 5 years) indicates a very successful outcome for the majority of LARS patients.

However, because LARS ligaments are relatively new, there is currently no long-term (10 years+) data on the success of these ligaments over time. Additionally, LARS ligaments require the drilling of much larger bone tunnels than auto- or allografts, making revision of a failed reconstruction more difficult.
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舊 2012-07-06, 17:14   #22
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Rehab and Recovery

What to expect from rehab
Remember, surgery is the easy part. The hard work - and ultimately, your successful return to the slopes - depend on your dedication to rehab.

First of all, find yourself a good physiotherapist who has plenty of experience with ACL rehabilitation. Secondly, make sure you follow your surgeon's protocol and physiotherapist's instructions to the letter. The graft will be fragile at first, and the limitations of early rehab - which rapidly become frustrating as your mobility and strength increase - are specifically designed to protect it.

Make sure you are prepared to be quite immobile for at least a few days after surgery. Rest in the early stages is critical to the healing process. Don't make anything harder than it needs to be.

Physically, the first few days after surgery are the hardest. You'll spend most of this time lying down with your leg elevated; it's important to keep the knee above the heart (this encourages blood to drain out of the knee, reducing swelling) and to ice regularly. A cryocuff (a simple machine that allows you to continuously cool and compress the joint) is an excellent investment that is worth its weight in gold at this stage, as you can fill it with ice and it's good for 6-8 hours. This saves trips to the freezer for additional ice packs. Don't be tempted to put a pillow under the knee when you're resting or sleeping, even though this is the most comfortable position to be in. This encourages the knee to stay in a slightly bent position, which isn't a good idea when you're trying to regain extension (critical to walking with a normal gait, and one of the most important things after ACL surgery). Putting a pillow or prop under the ankle and leaving the knee unsupported allows gravity to encourage it into full extension.

In addition to pain from the surgery sites, something that's often overlooked is the "blood rush." This is where the surgical haematoma rushes down the leg when you go from a sitting to a standing position, and it causes pain in the calf that can be excruciating. It can't be entirely avoided, but moving very slowly to an upright position will help. If the pain seems unusually severe or persistent, don't hesitate to ask your OS or family doctor to take a look. Excessive pain, swelling and redness can all be signs of a DVT, so it's worth taking seriously.

You'll most likely experience lots of other additional aches and pains, and sensations so strange you have no idea how your leg could be producing them. (ACL surgery often involves severing a nerve, which leads to a lot of very unusual sensations as the nerve responds and regenerates.)

Early rehab exercises focus on regaining flex and extension while giving the joint time to heal. Later exercises work on restoring strength, and ultimately preparing for a return to activity. It's a long process, and at times can seem incredibly frustrating. Remember - it's a marathon, not a sprint, and it will be worth it in the end.

The following is an example of a standard ACL rehab protocol. Your individual protocol may vary depending on your surgeon's preferences and the type of graft used in your reconstruction.

Phase I: Pre-Operative Phase
Goals:
a) Restore normal motion of knee
b) Restore normal walking
c) Mentally prepare for surgery

Exercises:
a) Stretching, active assisted range of motion (movement of knee with help), pushing knee into extension (straighten).
b) Muscular strengthening
c) Balance training
d) Other physical therapy activities

Phase II: Immediate Post-Operative (Day 1 - Day 7)
Goals:
a) Reduce and control swelling and pain
b) Restore full passive knee extension (straighten)
c) Bend knee to at least 90 degrees
d) Walking with brace

Exercises:
a) Active movementof knee through partial range of motion
b) Tighten quad muscles with straight knee
c) Straight leg raises
d) Toe calf raises
e) Weight shifting, small squats and lunges
f) Walking

Phase III: Controlled phase (Weeks 2-3)
Goals:
a) Maintain full passive knee extension (fully straightened knee)
b) Progress flex of knee to 115-125 degrees
c) Reduce swelling
d) Improve muscle strength

Exercises:
a) Straighten knee with physical therapist helping pushing it straight
b) Leg press and hamstring curls
c) Toe calf raises and wall squats
d) Lunges (forward and to side)
e) Balance drills, stationary bike, pool program

Phase IV: Intermediate phase (Weeks 3-6)
Goals:
a) Improve leg strength
b) Improve muscle control and endurance
c) Normalize knee movements
d) Perform more functional activities

Exercises:
a) Step-up / step-downs
b) Lunges and squats
c) Leg press and toe calf raises
d) Hip strengthening
e) Balance and endurance training
f) Agility drills in pool

Phase V: (Advanced strengthening phase (Weeks 7-12)
Goals:
a) Maintain motion
b) Protect knee joint and cartilage in knee
c) Maximize leg strengthening
d) Promote more functional activities

Exercises:
a) Step-up / step-down on balance beam
b) Squats on uneven/unstable surfaces
c) Double and single leg jumps
d) Rotation movements at the knee
e) Agility drills with sideways and backward movements

Phase VI: Return to activity phase (Week 10/12 and beyond)
Goals:
a) Gradual return to sport activities
b) Continue muscular strengthening and endurance training

Exercises:
a) Lunges and advanced balance activities
b) Elliptical, cycling and running
c) Returning to skiing and other sports

*Must meet criteria set by physical therapist before returning to sport activities.
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舊 2013-04-29, 09:01   #23
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This video is explains the anatomy of the knee:

http://www.eorthopod.com/videos/anatomy-knee

and about ACL

http://www.eorthopod.com/videos/ante...ament-injuries
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舊 2013-11-08, 05:36   #24
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Surgeons describe new ligament in the human knee

An article recently published in KU Leuven :-

Two knee surgeons at University Hospitals Leuven have provided the first full anatomical description of a previously enigmatic ligament in the human knee. The ligament appears to play an important role in patients with ACL tears.

Despite successful ACL repair surgery and rehabilitation, some patients with ACL-repaired knees continue to experience so-called 'pivot shift', or episodes where the knee 'gives way' during activity. For the last four years, orthopaedic surgeons Dr Steven Claes and Professor Dr Johan Bellemans have been conducting research into serious ACL injuries in an effort to find out why. Their starting point: an 1879 article by a French surgeon that postulated the existence of an additional ligament located on the anterior of the human knee.

That postulation turned out to be correct: the Belgian doctors are the first to provide a full anatomical description of the ligament after a broad cadaver study using macroscopic dissection techniques. Their research shows that the ligament, called the anterolateral ligament (ALL), was noted to be present in all but one of the 41 cadaveric knees studied. Subsequent research shows that pivot shift, the giving way of the knee in patients with an ACL tear, is caused by an injury in the ALL ligament.

‪Some of the researchers' conclusions were recently published in the Journal of Anatomy. The Anatomical Society praised the research as "very refreshing" and commended the researchers for reminding the medical world that, despite the emergence of advanced technology, our knowledge of the basic anatomy of the human body is not yet exhaustive.

‪Some of the researchers' conclusions were recently published in the Journal of Anatomy. The Anatomical Society praised the research as "very refreshing" and commended the researchers for reminding the medical world that, despite the emergence of advanced technology, our knowledge of the basic anatomy of the human body is not yet exhaustive.

‪The research questions current medical thinking about serious ACL injuries and could signal a breakthrough in the treatment of patients with serious ACL injuries. Dr Claes and Professor Bellemans are currently working on a surgical technique to correct ALL injuries. Those results will be ready in several years.

http://www.kuleuven.be/english/news/...the-human-knee
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