The information that follows includes the details of anterior cruciate ligament (ACL) anatomy and the pathophysiology of an ACL tear, treatment options for ACL injuries along with a description of ACL surgical techniques and rehabilitation, potential complications, and outcomes. The information is intended to assist the patient in making the best-informed decision possible regarding the management of ACL injury.
Anatomy
The bone structure of the knee joint is formed by the femur, the tibia, and the patella. The ACL is one of the four main ligaments within the knee that connect the femur to the tibia.
The knee is essentially a hinged joint that is held together by the medial collateral (MCL), lateral collateral (LCL), anterior cruciate (ACL) and posterior cruciate (PCL) ligaments. The ACL runs diagonally in the middle of the knee, preventing the tibia from sliding out in front of the femur, as well as providing rotational stability to the knee.
The weight-bearing surface of the knee is covered by a layer of articular cartilage. On either side of the joint, between the cartilage surfaces of the femur and tibia, are the medial meniscus and lateral meniscus. The menisci act as shock absorbers and work with the cartilage to reduce the stresses between the tibia and the femur.
Description
The anterior cruciate ligament (ACL) is one of the most commonly injured ligaments of the knee. In general, the incidence of ACL injury is higher in people who participate in high-risk sports, such as basketball, football, skiing, and soccer.
Approximately half of ACL injuries occur in combination with damage to the meniscus, articular cartilage, or other ligaments. Additionally, patients may have bruises of the bone beneath the cartilage surface. These may be seen on a magnetic resonance imaging (MRI) scan and may indicate injury to the overlying articular cartilage.
Cause
It is estimated that the majority of ACL injuries occur through non-contact mechanisms, while a smaller percent result from direct contact with another player or object.
The mechanism of injury is often associated with deceleration coupled with cutting, pivoting or sidestepping maneuvers, awkward landings or “out of control” play.
Several studies have shown that female athletes have a higher incidence of ACL injury than male athletes in certain sports. It has been proposed that this is due to differences in physical conditioning, muscular strength, and neuromuscular control. Other hypothesized causes of this gender-related difference in ACL injury rates include pelvis and lower extremity (leg) alignment, increased ligamentous laxity, and the effects of estrogen on ligament properties.
Natural History
What happens naturally with an ACL injury without surgical intervention varies from patient to patient and depends on the patient’s activity level, degree of injury and instability symptoms.
The prognosis for a partially torn ACL is often favorable, with the recovery and rehabilitation period usually at least 3 months. However, some patients with partial ACL tears may still have instability symptoms. Close clinical follow-up and a complete course of physical therapy helps identify those patients with unstable knees due to partial ACL tears.
Complete ACL ruptures have a much less favorable outcome without surgical intervention. After a complete ACL tear, some patients are unable to participate in cutting or pivoting-type sports, while others have instability during even normal activities, such as walking. There are some rare individuals who can participate in sports without any symptoms of instability. They are able to “cope” with their ACL deficient knee. This variability is related to the severity of the original knee injury, as well as the physical demands of the patient.
About half of ACL injuries occur in combination with damage to the meniscus, articular cartilage or other ligaments. Secondary damage may occur in patients who have repeated episodes of instability due to ACL injury. With chronic instability, a large majority of patients will have meniscus damage when reassessed 10 or more years after the initial injury. Similarly, the prevalence of articular cartilage lesions increases in patients who have a 10-year-old ACL deficiency.
Nonsurgical Treatment
In nonsurgical treatment, progressive physical therapy and rehabilitation can restore the knee to a condition close to its pre-injury state and educate the patient on how to prevent instability. This may be supplemented with the use of a hinged knee brace. However, many people who choose not to have surgery may experience secondary injury to the knee due to repetitive instability episodes.
Surgical treatment is usually advised in dealing with combined injuries (ACL tears in combination with other injuries in the knee). However, deciding against surgery is reasonable for select patients. Nonsurgical management of isolated ACL tears is likely to be successful or may be indicated in patients:
- With partial tears and no instability symptoms
- With complete tears and no symptoms of knee instability during low-demand sports who are willing to give up high-demand sports
- Who do light manual work or live sedentary lifestyles
Surgical Treatment
ACL tears are not usually repaired using suture to sew it back together, because repaired ACLs have generally been shown to fail over time. Therefore, the torn ACL is generally replaced by a substitute graft made of tendon.
- Patellar tendon autograft (autograft comes from the patient)
- Hamstring tendon autograft
- Quadriceps tendon autograft
Patient Considerations
Active adult patients involved in sports or jobs that require pivoting, turning or hard-cutting as well as heavy manual work are encouraged to consider surgical treatment. This includes physiologically older patients who have previously been excluded from consideration for ACL surgery.
Activity, not age, should determine if surgical intervention should be considered.
In young children or adolescents with ACL tears, early ACL reconstruction creates a possible risk of growth plate injury, leading to bone growth problems. But nowadays the surgeon can modify the ACL surgrical technique (all-inside physeal sparing techniques) to decrease the risk of growth plate injury in young patients with ACL injury.
A patient with a torn ACL and significant functional instability has a high risk of developing secondary knee damage and should therefore consider ACL reconstruction.
It is common to see ACL injuries combined with damage to the menisci, articular cartilage, collateral ligaments, joint capsule, or a combination of the above. The “unhappy triad,” frequently seen in football players and skiers, consists of injuries to the ACL, the MCL, and the medial meniscus.
In cases of combined injuries, surgical treatment may be warranted and generally produces better outcomes. As many as half of meniscus tears may be repairable and may heal better if the repair is done in combination with the ACL reconstruction.
Surgical Procedure
Before any surgical treatment, the patient is usually sent to physical therapy. Patients who have a stiff, swollen knee lacking full range of motion at the time of ACL surgery may have significant problems regaining motion after surgery. It usually takes three or more weeks from the time of injury to achieve full range of motion. It is also recommended that some ligament injuries be braced and allowed to heal prior to ACL surgery.
Arthroscopic Reconstruction of the torn ACL is usually performed under Spinal Anesthesia (a needle is used to place a numbing drug in your spinal canal to numb and temporarily immobilise your both lower extremity). The patient remains awake and can see the monitor and observe the entire surgical procedure.
The surgery usually begins with an examination of the patient’s knee while the patient is relaxed due the effects of anesthesia. This final examination is used to verify that the ACL is torn and also to check for looseness of other knee ligaments that may need to be repaired during surgery or addressed postoperatively.
If the physical exam strongly suggests the ACL is torn, the selected tendon is harvested and the graft is prepared to the correct size for the patient.
After the graft has been prepared, the surgeon places an arthroscope into the joint. Small (5mm) incisions called portals are made in the front of the knee to insert the arthroscope and instruments and the surgeon examines the condition of the knee. Meniscus and cartilage injuries are trimmed or repaired and the torn ACL stump is then removed.
In the most common ACL reconstruction technique, bone tunnels are drilled into the tibia and the femur to place the ACL graft in almost the same position as the torn ACL. The graft is pulled into position up through the tibial tunnel and then up into the femoral tunnel. The graft is held under tension as it is fixed in place using endobutton, interference screws, spiked washers, posts, or staples. The devices used to hold the graft in place are generally not removed and get integrated with the patient’s bone within a couple of years.
Variations on this surgical technique include the “two-incision,” “over-the-top,” and “double-bundle” types of ACL reconstructions, which may be used because of the preference of the surgeon or special circumstances (revision ACL reconstruction, open growth plates).
Before the surgery is complete, the surgeon will probe the graft to make sure it has good tension, verify that the knee has full range of motion and perform tests to assess graft stability. The skin is closed and dressings are applied and the knee is placed in an immobiliser.
Rehabilitation
Physical therapy is a crucial part of successful ACL surgery, with exercises beginning immediately after the surgery. Much of the success of ACL reconstructive surgery depends on the patient’s dedication to rigorous physical therapy. With new surgical techniques and stronger graft fixation, current physical therapy uses an accelerated course of rehabilitation.
Postoperative Course. In the first 10 to 14 days after surgery, the wound is kept clean and dry, and early emphasis is placed on regaining the ability to fully straighten the knee and restore quadriceps control.
The knee is iced regularly to reduce swelling and pain. Weight-bearing status (use of crutches to keep some or all of the patient’s weight off of the surgical leg) is also determined on case by case basis depending upon other injuries addressed at the time of surgery.
Rehabilitation. The goals for rehabilitation of ACL reconstruction include reducing knee swelling, maintaining mobility of the kneecap to prevent anterior knee pain problems, regaining full range of motion of the knee, as well as strengthening the quadriceps and hamstring muscles.
The patient may return to sports when there is no longer pain or swelling, when full knee range of motion has been achieved, and when muscle strength, endurance and functional use of the leg have been fully restored.
The patient’s sense of balance and control of the leg must also be restored through exercises designed to improve neuromuscular control. This usually takes 4 to 6 months. The use of a functional brace when returning to sports is ideally not needed after a successful ACL reconstruction, but some patients may feel a greater sense of security by wearing one.
Surgical Complications
Infection. The incidence of infection after arthroscopic ACL reconstruction is very low.
Bleeding, numbness. Rare risks include bleeding from portal sites and swelling inside the knee joint, which usually settle with conservative measures. It is not uncommon to have numbness of the outer part of the upper leg next to the incision, which is usually temporary and improves with time.
Blood clot. Although rare, blood clot in the veins of the calf or thigh is a potentially life-threatening complication. A blood clot may break off in the bloodstream and travel to the lungs, causing pulmonary embolism or to the brain, causing stroke.
Instability. Recurrent instability due to rupture or stretching of the reconstructed ligament or poor surgical technique and non-compliant rehabilitation is possible.
Stiffness. Knee stiffness or loss of motion has been reported by some patients after surgery.
Extensor mechanism failure. Rupture of the patellar tendon (patellar tendon autograft) or patella fracture (patellar tendon or quadriceps tendon autografts) may occur due to weakening at the site of graft harvest.
Growth plate injury. In young children or adolescents with ACL tears, early ACL reconstruction creates a possible risk of growth plate injury, leading to bone growth problems. This risk has been dramatically reduced with the use of All-inside physeal sparing techniques.
Knee Cap Pain. Postoperative anterior knee pain is especially common after patellar tendon autograft ACL reconstruction. The incidence of pain behind the kneecap varies greatly in studies, whereas the incidence of kneeling pain is often higher after patellar tendon autograft ACL reconstruction.
FATE OF ACL INJURY- DO ALL ACL TEARS NEED SURGERY??
The information that follows includes the details of anterior cruciate ligament (ACL) anatomy and the pathophysiology of an ACL tear, treatment options for ACL injuries along with a description of ACL surgical techniques and rehabilitation, potential complications, and outcomes. The information is intended to assist the patient in making the best-informed decision possible regarding the management of ACL injury.
Anatomy
The bone structure of the knee joint is formed by the femur, the tibia, and the patella. The ACL is one of the four main ligaments within the knee that connect the femur to the tibia.
The knee is essentially a hinged joint that is held together by the medial collateral (MCL), lateral collateral (LCL), anterior cruciate (ACL) and posterior cruciate (PCL) ligaments. The ACL runs diagonally in the middle of the knee, preventing the tibia from sliding out in front of the femur, as well as providing rotational stability to the knee.
The weight-bearing surface of the knee is covered by a layer of articular cartilage. On either side of the joint, between the cartilage surfaces of the femur and tibia, are the medial meniscus and lateral meniscus. The menisci act as shock absorbers and work with the cartilage to reduce the stresses between the tibia and the femur.
Description
The anterior cruciate ligament (ACL) is one of the most commonly injured ligaments of the knee. In general, the incidence of ACL injury is higher in people who participate in high-risk sports, such as basketball, football, skiing, and soccer.
Approximately half of ACL injuries occur in combination with damage to the meniscus, articular cartilage, or other ligaments. Additionally, patients may have bruises of the bone beneath the cartilage surface. These may be seen on a magnetic resonance imaging (MRI) scan and may indicate injury to the overlying articular cartilage.
Cause
It is estimated that the majority of ACL injuries occur through non-contact mechanisms, while a smaller percent result from direct contact with another player or object.
The mechanism of injury is often associated with deceleration coupled with cutting, pivoting or sidestepping maneuvers, awkward landings or “out of control” play.
Several studies have shown that female athletes have a higher incidence of ACL injury than male athletes in certain sports. It has been proposed that this is due to differences in physical conditioning, muscular strength, and neuromuscular control. Other hypothesized causes of this gender-related difference in ACL injury rates include pelvis and lower extremity (leg) alignment, increased ligamentous laxity, and the effects of estrogen on ligament properties.
Natural History
What happens naturally with an ACL injury without surgical intervention varies from patient to patient and depends on the patient’s activity level, degree of injury and instability symptoms.
The prognosis for a partially torn ACL is often favorable, with the recovery and rehabilitation period usually at least 3 months. However, some patients with partial ACL tears may still have instability symptoms. Close clinical follow-up and a complete course of physical therapy helps identify those patients with unstable knees due to partial ACL tears.
Complete ACL ruptures have a much less favorable outcome without surgical intervention. After a complete ACL tear, some patients are unable to participate in cutting or pivoting-type sports, while others have instability during even normal activities, such as walking. There are some rare individuals who can participate in sports without any symptoms of instability. They are able to “cope” with their ACL deficient knee. This variability is related to the severity of the original knee injury, as well as the physical demands of the patient.
About half of ACL injuries occur in combination with damage to the meniscus, articular cartilage or other ligaments. Secondary damage may occur in patients who have repeated episodes of instability due to ACL injury. With chronic instability, a large majority of patients will have meniscus damage when reassessed 10 or more years after the initial injury. Similarly, the prevalence of articular cartilage lesions increases in patients who have a 10-year-old ACL deficiency.
Nonsurgical Treatment
In nonsurgical treatment, progressive physical therapy and rehabilitation can restore the knee to a condition close to its pre-injury state and educate the patient on how to prevent instability. This may be supplemented with the use of a hinged knee brace. However, many people who choose not to have surgery may experience secondary injury to the knee due to repetitive instability episodes.
Surgical treatment is usually advised in dealing with combined injuries (ACL tears in combination with other injuries in the knee). However, deciding against surgery is reasonable for select patients. Nonsurgical management of isolated ACL tears is likely to be successful or may be indicated in patients:
- With partial tears and no instability symptoms
- With complete tears and no symptoms of knee instability during low-demand sports who are willing to give up high-demand sports
- Who do light manual work or live sedentary lifestyles
Surgical Treatment
ACL tears are not usually repaired using suture to sew it back together, because repaired ACLs have generally been shown to fail over time. Therefore, the torn ACL is generally replaced by a substitute graft made of tendon.
- Patellar tendon autograft (autograft comes from the patient)
- Hamstring tendon autograft
- Quadriceps tendon autograft
Patient Considerations
Active adult patients involved in sports or jobs that require pivoting, turning or hard-cutting as well as heavy manual work are encouraged to consider surgical treatment. This includes physiologically older patients who have previously been excluded from consideration for ACL surgery.
Activity, not age, should determine if surgical intervention should be considered.
In young children or adolescents with ACL tears, early ACL reconstruction creates a possible risk of growth plate injury, leading to bone growth problems. But nowadays the surgeon can modify the ACL surgrical technique (all-inside physeal sparing techniques) to decrease the risk of growth plate injury in young patients with ACL injury.
A patient with a torn ACL and significant functional instability has a high risk of developing secondary knee damage and should therefore consider ACL reconstruction.
It is common to see ACL injuries combined with damage to the menisci, articular cartilage, collateral ligaments, joint capsule, or a combination of the above. The “unhappy triad,” frequently seen in football players and skiers, consists of injuries to the ACL, the MCL, and the medial meniscus.
In cases of combined injuries, surgical treatment may be warranted and generally produces better outcomes. As many as half of meniscus tears may be repairable and may heal better if the repair is done in combination with the ACL reconstruction.
Surgical Procedure
Before any surgical treatment, the patient is usually sent to physical therapy. Patients who have a stiff, swollen knee lacking full range of motion at the time of ACL surgery may have significant problems regaining motion after surgery. It usually takes three or more weeks from the time of injury to achieve full range of motion. It is also recommended that some ligament injuries be braced and allowed to heal prior to ACL surgery.
Arthroscopic Reconstruction of the torn ACL is usually performed under Spinal Anesthesia (a needle is used to place a numbing drug in your spinal canal to numb and temporarily immobilise your both lower extremity). The patient remains awake and can see the monitor and observe the entire surgical procedure.
The surgery usually begins with an examination of the patient’s knee while the patient is relaxed due the effects of anesthesia. This final examination is used to verify that the ACL is torn and also to check for looseness of other knee ligaments that may need to be repaired during surgery or addressed postoperatively.
If the physical exam strongly suggests the ACL is torn, the selected tendon is harvested and the graft is prepared to the correct size for the patient.
After the graft has been prepared, the surgeon places an arthroscope into the joint. Small (5mm) incisions called portals are made in the front of the knee to insert the arthroscope and instruments and the surgeon examines the condition of the knee. Meniscus and cartilage injuries are trimmed or repaired and the torn ACL stump is then removed.
In the most common ACL reconstruction technique, bone tunnels are drilled into the tibia and the femur to place the ACL graft in almost the same position as the torn ACL. The graft is pulled into position up through the tibial tunnel and then up into the femoral tunnel. The graft is held under tension as it is fixed in place using endobutton, interference screws, spiked washers, posts, or staples. The devices used to hold the graft in place are generally not removed and get integrated with the patient’s bone within a couple of years.
Variations on this surgical technique include the “two-incision,” “over-the-top,” and “double-bundle” types of ACL reconstructions, which may be used because of the preference of the surgeon or special circumstances (revision ACL reconstruction, open growth plates).
Before the surgery is complete, the surgeon will probe the graft to make sure it has good tension, verify that the knee has full range of motion and perform tests to assess graft stability. The skin is closed and dressings are applied and the knee is placed in an immobiliser.
Rehabilitation
Physical therapy is a crucial part of successful ACL surgery, with exercises beginning immediately after the surgery. Much of the success of ACL reconstructive surgery depends on the patient’s dedication to rigorous physical therapy. With new surgical techniques and stronger graft fixation, current physical therapy uses an accelerated course of rehabilitation.
Postoperative Course. In the first 10 to 14 days after surgery, the wound is kept clean and dry, and early emphasis is placed on regaining the ability to fully straighten the knee and restore quadriceps control.
The knee is iced regularly to reduce swelling and pain. Weight-bearing status (use of crutches to keep some or all of the patient’s weight off of the surgical leg) is also determined on case by case basis depending upon other injuries addressed at the time of surgery.
Rehabilitation. The goals for rehabilitation of ACL reconstruction include reducing knee swelling, maintaining mobility of the kneecap to prevent anterior knee pain problems, regaining full range of motion of the knee, as well as strengthening the quadriceps and hamstring muscles.
The patient may return to sports when there is no longer pain or swelling, when full knee range of motion has been achieved, and when muscle strength, endurance and functional use of the leg have been fully restored.
The patient’s sense of balance and control of the leg must also be restored through exercises designed to improve neuromuscular control. This usually takes 4 to 6 months. The use of a functional brace when returning to sports is ideally not needed after a successful ACL reconstruction, but some patients may feel a greater sense of security by wearing one.
Surgical Complications
Infection. The incidence of infection after arthroscopic ACL reconstruction is very low.
Bleeding, numbness. Rare risks include bleeding from portal sites and swelling inside the knee joint, which usually settle with conservative measures. It is not uncommon to have numbness of the outer part of the upper leg next to the incision, which is usually temporary and improves with time.
Blood clot. Although rare, blood clot in the veins of the calf or thigh is a potentially life-threatening complication. A blood clot may break off in the bloodstream and travel to the lungs, causing pulmonary embolism or to the brain, causing stroke.
Instability. Recurrent instability due to rupture or stretching of the reconstructed ligament or poor surgical technique and non-compliant rehabilitation is possible.
Stiffness. Knee stiffness or loss of motion has been reported by some patients after surgery.
Extensor mechanism failure. Rupture of the patellar tendon (patellar tendon autograft) or patella fracture (patellar tendon or quadriceps tendon autografts) may occur due to weakening at the site of graft harvest.
Growth plate injury. In young children or adolescents with ACL tears, early ACL reconstruction creates a possible risk of growth plate injury, leading to bone growth problems. This risk has been dramatically reduced with the use of All-inside physeal sparing techniques.
Knee Cap Pain. Postoperative anterior knee pain is especially common after patellar tendon autograft ACL reconstruction. The incidence of pain behind the kneecap varies greatly in studies, whereas the incidence of kneeling pain is often higher after patellar tendon autograft ACL reconstruction.
