Intro (157w): Within the intracapsular of the patella lies the Cruciate Ligaments. The two cruciate ligaments are known as the Posterior cruciate ligament and the anterior cruciate ligament (ACL). When the bones in the leg, the femur and tibia, twist in opposite directions, an ACL injury may occur. ‘The ACL is a band of dense connective tissue, connecting the femur to the tibia. It resists anterior tibial translation and rotational loads. The two components of the ACL is the anteromedial bundle and the posterolateral bundle.’ ( ‘An isolated rupture of the ACL can occur from a forceful internal rotation of the femur, the ligament impinges at the anterior aspect of the intercondylar notch. When skiing, the application of a passive anterior drawer applied by the posterior shell of the ski boot, as well as the use of strong quadriceps contracting to assist with recovery after a jump or prior to a possible fall can result in an ACL rupture.’ (
Epidemiology (348w):
One of the most common skiing injuries is ACL rupture. “Comprising 20-30% of all skiing injuries”( Laporte, Binet, & Constans, 2000; Pujol, Blanchi, & Chambat, 2007).( Lower limb injuries have decreased in skiing. “Tibia and ankle fractures have decreased by 90%” ( However, the number of ACL injuries does not follow this trend, and in fact have increased. A process of ACL injury that is well analyzed is when the strength of the quadricep muscle is strong enough to displace the tibia. This muscle is activated when the performer wishes to regain balance post landing a jump, however when the muscle is powerful this can overcompensate, causing a tear in the ACL. ‘McConkey studied 15 expert skiers who experienced ACL ruptures due to the contraction of the quadricep muscle, due to an out-of-control sitting-back position or to regain control post landing from a jump. After 5 years, Geyer and Wirth analyzed isolated ACL ruptures which were caused by regaining balance post jump landings, which results in the anterior displacement of the tibia, rupturing the ACL.’ ( There are many other ways that ACL injuries could occur whilst skiing. This injury could be due to a poor landing post jump; leaning back whilst out of control, resulting in the quadricep muscle overworking; or a twisting of the knee, possibly due to catching the inside edge of the ski or a slow turn in heavy and deep snow. ‘Internal and external tibial torque applied to the knee, whilst at different flexion angles can cause ACL injuries. Jarvinen studied 51 patients who sustained ACL ruptures whilst skiing. 47% of these skiers reported a valgus-external rotation mechanism, whilst 41% reported a flexion-internal rotation mechanism. Whilst additional skiers described a hyperextension-internal rotation mechanism.’ ( The three ways mentioned are the valgus-external rotation mechanism, which is when the tibia angles to the lateral side whilst completing external rotation. Flexion-internal rotation mechanism is when the tibia internally rotates on the femur, whilst the knee joint is flexed, and finally hyperextension-internal rotation mechanism is when the knee is fully locked out, and the tibia rotates internally.

There are three type of ACL injuries, two where only the ACL is ruptured and one where there are multiple injuries. The first is when a posterior force pushed the tibia forward, causing the ligament to tear, the second is when the femur internally rotates, causing the ligament to impinge on the intercondylar notch. The third injury not only ruptures the ACL, but also causes damage to the medial collateral ligament and results in a tear of the medial meniscus, this occurs when internal or external tibial torque is applied to the knee at various flexion angles. “The “Quadriceps drawer” theory suggests that the quadriceps muscles, through the patellar ligament, will pull the tibia forward relative to the femur. This effect is highest at low knee flexion angles. Valgus bending, internal rotation and vertical compression are other suggested mechanisms that have been suggested to load the ACL.” (
“External forces were mainly (75%) responsible for this loading. The contribution of the fully activated quadriceps muscles was only 25%. It was concluded that the model could reproduce a typical landing movement and is therefore considered to be sufficiently realistic.” ( External factors that can influence this injury include the equipment used by the individual, such as the binding setting used by the performer, as if the binding is adapted for a more able skier the foot may not release from the ski as easily during an incident, causing the knee to twist. “With the increased popularity of carving skis an increase in the knee injury rate has been expected.” ( factor is the snow conditions, as if the conditions dramatically change throughout the slope the skier may react poorly to this, resulting in a loss of balance and control. The speed of the athlete as well as the preparation are also vital factors. “Most of the injuries occurred in a slip- catch situation while the athlete was still skiing, without or before falling. This injury situation develops rapidly because of high skiing speeds. With aggressively carving skis and aggressive snow conditions, large forces are generated when the inside edge catches the snow surface.” ( Internal factors include the individuals gender, “About one-third of injured males and 50% of injured females suffer from a knee injury in recreational alpine skiing. Regarding ACL injuries, recreational female skiers are 2.4–3.3 times more likely to injure their ACL than their male counterparts.” ( The suggested reason for this is due to anatomical and neuromuscular differences, as well as hormonal factors. Another internal factor is the intercondylar notch. ‘This could either be because of the difference between the notch width and ligament width, which impacts the strength. The second theory is that the narrow intercondylar notch may lead to impingement of the ACL on the medial part of femoral condyle.’ HYPERLINK “”
Rehabilitation (464/250w): – maybe rephrase using the isokinetic stages?
The important achievements of treatment include restoration of knee stability, limit surgical morbidity along with returning to activities successfully. Once an ACL rupture has occurred the individual must ensure that plenty of rest, ice, compression and elevation occurs. This aims to reduce pain and swelling of the joint. However, to attempt to fully recover from this injury an operation is often inevitable. This process often involves the ‘graft of the mid-third autogenous patellar tendon, used to reconstruct the ACL.’ ( There are three methods used to reconstruct the ACL, autogenous; allography and xenographic. The most common is autogenous, which is where the surgeon will remove a segment of tendon from elsewhere, usually the hamstring or patella tendon, and attach it where the ACL was. This uses arthroscopic reconstruction, which reduces chance of infection as well as other complications as it is less destructive around the joint and ligament. The tendon is attached to the bone using screws to ensure effectiveness post operation. Post operation there are steps to follow to assist with effective recovery. The main objective to achieve during rehabilitation is full knee extension, although not achieving this doesn’t reduce stability, it can result in anterior knee pain and weakened quadriceps, which eventually lead to a poor functioning knee. K. Donald Shelbourne, M.D has produced a four stage rehabilitation process. The initial stage is prior to the operation and is key to a successful recovery, the important factor of this stage is that the knee does not display swelling and demonstrates a normal range of motion. “Operating on an acutely injured knee without restoring full knee extension preoperatively is associated with an increased incidence of postoperative knee stiffness.” (;acdnat=1543175308_13c25da41819507d32ee9a9bd9856411) The second phase targets the couple of weeks following surgery and recommends four goals, minimising swelling; achieving full knee extension; allowing to flex the knee to 90 and establishing quadricep control. A continuous passive motion machine is advised to elevate the knee and aid in comfort for the patient. Along with this, extension exercises are vital to ensure there is no permanent loss of knee motion and to reduce difficult when the individual returns to activity. The third phase covers week two to five. There are four targets to achieve, normal gait pattern; continuation of full knee extension; increased knee flexion and improving quadricep strength. “Flexion exercises such as wall slides are continued, but the importance of maintaining full knee extension must be emphasized. Quadriceps strengthening is also an important part of preparing for a return to sport specific activities.” (;acdnat=1543175308_13c25da41819507d32ee9a9bd9856411) The final stage is returning to exercise, is it necessary that the quadricep strength has returned to 70% of its original strength, “. Any attempt to return before this level of strength is obtained often results in a sore and swollen knee” (;acdnat=1543175308_13c25da41819507d32ee9a9bd9856411)