The anterior cruciate ligament (ACL) is a critical structure in knee kinematics because it resists translational and rotational loads on the front of the tibia. The ACL provides approximately 85% of the total binding force of anterior translation. It also prevents excessive medial and lateral tibia Rotation and varus and valgus stress . Nonetheless, due to the presence of mechanoreceptors in the ligament, its primary role is proprioceptive function . Therefore, ACL injury may be viewed as a neurophysiological dysfunction rather than simply peripheral Musculoskeletal injury.  Due to its complex role in knee kinematics, clinical symptoms and subjective instability when ACL injury occurs, a comprehensive rehabilitation program is required . ACL injuries are the most common knee joint Athletes and women are 2 to 8 times more likely to suffer an ACL injury than male athletes.
Injuries range from mild (such as a small tear/sprain) to severe (when the ligament is completely torn) . Surgical retraction is required when the ACL is completely ruptured and there are clinical and subjective signs of instability. However, ACLs are not self-evident Reconstruction will automatically lead to a return to the pre-injury level of activity.
ACL rehabilitation is suitable for both conservative and surgical treatment.
See these pages for related ACL injuries
Clinically Relevant Anatomy
The anterior cruciate ligament (ACL) is a dense band of connective tissue that extends from the femur to the tibia. The ACL originates from the posteromedial corner of the medial lateral femoral condyle of the intercondylar notch and ends anterior to the intercondylar process. The tibia fuses with the anterior horn of the medial meniscus. As the ACL travels from the femur to the tibia, the ACL passes through the joint anteromedially and distally. As it does so, it turns in a slight outward (lateral) spiral.
The density of blood vessels within the ligament is not uniform. In the ACL, the avascular zone is located in the anterior fibrocartilage with the ligament facing the anterior border of the intercondylar notch . Malvascularity and Coincidence of Existence Fibrocartilage is also found in gliding tendons in areas of compressive load, which play a role in the poor healing capacity of the ACL. 
See the following pages for related anatomy: Anterior Cruciate Ligament (ACL) and Anterior Cruciate Ligament (ACL) – Structural and Biomechanical Properties
ACL rehabilitation has changed considerably over the past decade. Intensive research into the biomechanics of injured and operated knees has led to a shift from an early 1980s technique characterized by post-operative cast delayed weight-bearing and Range of motion (ROM) is limited in the current early rehabilitation program with immediate ROM training and weight-bearing exercises .
ACL rehabilitation is suitable for both conservative and surgical treatment. Conservative management of ACL injuries may be the best option for sedentary patients. Indeed, the patient’s age, physical activity and the most important symptoms of subjective instability in activities of daily living should be considered Decide for or against ACL reconstruction . In these cases, a physiotherapy program to fully restore ROM, a comprehensive program to strengthen and restore proprioception, and training for normal gait patterns may be the best rehabilitation options. However, if symptoms are unstable The knee joint is not reduced after physiotherapy or after adjusting the range of motion, and anterior cruciate ligament reconstruction is recommended. This may prevent multiple interventions due to further meniscal and cartilage damage .
It is useful to remember that ACL injuries rarely occur in isolation. The presence and extent of other injuries may affect how ACL injuries are managed. In fact, the mechanism of injury can also damage the medial collateral ligament (MCL) or the meniscus. other related injuries There may be microfractures or bone contusions with or without cartilage damage.  In these cases, ACL rehabilitation programs must not be standardized and take into account comorbidities.
The main goals of general rehabilitation of the knee from an ACL injury are:
- Gain full ROM of the knee
- Repair muscle strength and proprioception
- Gaan in good functional stability
- Reach the best possible functional level (walking, running, jumping…)
- Decrease the risk for re-injury
- (Return to sport)
Phases of ACL rehabilitation
Physiotherapy intervention can be divided into several phases:
- Acute Stage
- Preoperative stage or conservative treatment
- Post-surgical Stage
- Return to sport
Following an ACL injury, with or without surgery, physical therapy management focuses on restoring range of motion intensity, proprioception, and stability. PRICE or PEACE AND LOVE should be used in the acute phase to reduce swelling and pain to try the full range Exercise and reduce joint effusion. Appropriate anti-inflammatory medications are used to help control pain and swelling .
Indications for crutches and eventual use of knee immobilizers may apply to some patients. However, long-term use of knee immobilizers should be limited to avoid quadriceps atrophy .
Neuromuscular inhibition of the quadriceps femoris due to intra-articular effusion may negatively impact reinforcement. In any case, the exercises should encourage range of motion, initially strengthening the quadriceps and hamstrings, and ultimately strengthening proprioception . In fact, the strength and Proprioceptive alterations occur in both injured and uninjured limbs . To assist with preoperative optimization, the following guidelines are recommended in the acute and early subacute phases after injury:
- Full extension is obtained by doing:
- Passive knee extension: Physical therapists can provide passive knee extension through manual therapy and teaching exercises that add leverage to gently force extension
- Patellar self-mobilisations,
- Heel Props,
- Prone hang exercise,
- Static quads/SLR;
- Bending (Flexion) is obtained by doing:
- Passive Knee Flexion: Physical therapists can provide passive knee flexion through manual therapy and teaching exercises, adding leverage to gently flex
- Prone Knee Bend (Light Kick Exercise)
- Wall slides,
- Heel slides;
- Knee flexion/extension in sitting;
- Ankle DF/PF/circumduction;
- Glutes medius work in side lying;
- Gluteal exercises in prone;
- Weight transfer while standing (front/back/side).
It has also been shown that neuromuscular electrical stimulation (NMES) combined with exercise is more effective in improving quadriceps strength than exercise alone .
It may also be useful to consider the use of tape to provide stability and encourage swelling reduction .
There is no clear transition from acute to preoperative, and each phase may last days or months before surgery. Instructionally, the end of the acute phase occurs when the patient returns to knee extension and at least 110 degrees of full range of motion. Flexion or near-normal gait pattern.
Before Surgical Stage
The highest incidence of knee stiffness occurs when ACL surgery is performed when the knee is swollen and painful and has limited range of motion.
If surgery is delayed until the acute inflammatory period has passed, the swelling has subsided, a normal or near-normal range of motion (especially stretching) is obtained and the gait pattern has passed Reconstructed . However, practical guidelines agree that the indication for reconstruction is persistent knee instability and complaints of giving way. This diagnosis is difficult to make in an acute setting. Guidelines recommend that The first week after trauma to minimize the risk of surgery in asymptomatic patients.
Once the acute phase is over, it is important to prepare the knee for surgery and optimize the outcome as much as possible. The focus needs to be on strength and proprioception. Still, physical therapists must keep the injured knee stationary to improve range of motion minimal swelling.
RICE and electrotherapy can be applied a few weeks before surgery to gain a full range of motion and reduce joint effusion. The patient should also have a normal gait pattern: as it is useful to analyze leg movements during the swing phase of walking And in the one-legged stance phase. Thereby helping patients recover faster movement and strength after surgery .
The length of this pre-operative phase can last a few days or weeks. Therefore, the role of the physiotherapist is also to maintain the compliance of the patient. For this reason, rehabilitation programs must have measurable weekly goals to improve muscle strength and Adjust for range of motion and improve proprioception. This will provide new goals to be achieved each week: patients who achieve these goals will maintain adherence to treatment .
During the preoperative phase, it is important to provide different approaches to enhance muscle strength and proprioception. Therefore, offering patients two different exercise programs to perform at the gym and at home may be a good solution. However, given Submaximal load on the injured knee to avoid knee swelling or re-injury due to lack of proprioception.
- Gain and maintain a full range of motion in extension and continuously improve the range of motion in flexion with minimal swelling;
- Building muscle strength: Once you reach 110 degrees of flexion, you can begin building muscle strength. An example of the exercise is as follows:
- Swimming (avoid breaststroke),
- Low-impact exercise equipment such as elliptical cross trainers stationary bikes and treadmills
- Leg press machine,
- Leg curl machine or leg extension machine (see Open Kinetic Chain below)
- Weight-bearing exercises such as squat lunges (see closed kinetic chain exercises below);
- Improve proprioception:
- One-leg- standing exercise
- One-legged stance exercises to add balance pads or cues to the arms (throwing or catching the ball to the target…)
- Single-leg standing exercise in different planes (frontal sagittal plane)
- Preparation for controlled jumps;
- maintain a high level of adherence to the rehabilitation program ;
- Psychological preparation: The patient must know what to expect from the surgery and understand the recovery phase after surgery. 
See these pages for related ACL rehabilitation: acute management after surgery
ACL reconstruction has changed considerably over the past decade. Various tissues/grafts have been used for anatomical reconstruction of torn ACLs. The most commonly used are autografts (patella and hamstrings) and sometimes allografts (taken from cadavers). Ligamentation process of grafts require precautions in terms of loading and physical requirements.  However, it seems to indicate that the transformation of new ACLs is a process lasting 9 years or more. Furthermore, this appears to be an adaptation process rather than a complete recovery.  Nevertheless, there are still There were no substantial differences in physiotherapy between grafts in the postoperative period.
Consider pain, swelling, muscle contractures, limiting range of motion, and abnormal gait patterns as indicators of good outcomes. In the postoperative phase, three factors are important:
- Early terminal knee extension equals contralateral
- Early weight bearing,
- Closed and open kinetic chain strengthening exercises.
Early knee extension lays the foundation for the entire rehabilitation program.
The incidence of knee flexion contracture with quadriceps weakness and dysfunction of the extensor mechanism after ACL reconstruction was significantly reduced with the immediate postoperative acceleration of knee extension.
According to the ACL Rehabilitation Guidelines, a good physical therapy program depends on achieving weekly goals.
- Regular icing and elevation are used to reduce swelling . Final medication or pain reliever according to MD attempt rehabilitation goals.
- The goal is to have a full extension and flexion of 70 degrees by the end of the first week.
- Use knee braces and crutches that are consistent with your surgeon only when needed. In fact, there is no additional therapeutic value in wearing a knee brace after ACL reconstruction . The authors gradually reduced the use of knee pads.   Postoperative rehabilitation brace Extending or opening the hinge for the ROM has no significant advantage over no support.  The need for postoperative functional support and the consensus regarding the duration of support has been questioned in many rehabilitation programs. Harilainen et al compared Influence of functional bracing on postoperative non-bracing after patella graft ACL reconstruction. There were no significant differences in functional outcome stability or isokinetic muscle torque between the two groups at 1 and 2 years postoperatively . in a similar Risberg et al. found no significant differences in knee laxity, muscle strength, range of motion on tests of knee function, or pain. 
- Multidirectional movement of the patella should be included for at least 8 weeks. Additional activities for the first 4 weeks were passive extension of the knee (without hyperextension) and passive and active flexion activities.
- Strengthening exercises for the calf muscles, the hamstrings and the quadriceps (vast medialis) can be performed on the back or stomach.
- Isometric quadriceps exercises are safe from the first week after surgery 
Early weight bearing appears to be beneficial and may reduce patellofemoral pain. Early exercise is safe and may help avoid problems with joint fibrosis later in life. Continuous passive movement does not improve patient outcomes. Selected Minimum Supervised Physical Therapy Proactive patients appear to be safe with no apparent risk of complications .
ACL Reconstruction: Rehabilitation Program Workshop  Heel Lift for ACL Reconstruction 
- There is no evidence that icing and elevation are helpful after week 1.
- The first goal is to maintain full extension and increase flexion each week.
- Try to really increase the standing phase, try walking with one crutch. With good hamstring/quad control, crutch use can be reduced earlier.
- Strengthening exercises for the calf muscles, hamstrings, and quadriceps (femoris medialis) can be done using a stationary bike or a lightweight seated position. Progression of movement depends on painful swelling and control of the quadriceps.
- Eccentric quadriceps training (in CKC) started 3 weeks after ACLR safety resulted in greater improvement in quadriceps strength compared with concentric training 
- In some patients with good hamstring/quadriceps control, some exercises in closed kinetic chains can really be tried (half-squat hip hinge calf strengthening…). Typically, these exercises are performed by patients who have been trained for a long time in a good preoperative phase program.
Quadriceps strength is enhanced with early stretches and weights. The combination of early knee extension, early weight bearing and closed kinetic quadriceps strengthening allows patients to progress at a fairly rapid rate during post-operative rehabilitation without the need for Impairs ligament stability. 
- Passive mobilization should normalize movement, but flexion should not be complete.
- In both open-chain and closed-chain exercises, you can start training your hamstrings and quads at higher intensities. Exercises should start at light intensity (50% of maximum strength) and now gradually increase to 60-70%. Closed-chain exercises should be built on less accountable foundations position (leg press step) to a more crowded starting position (eg squad). Progression of movement depends on painful swelling and control of the quadriceps.
- Proprioception and coordination exercises can develop if overall strength is good. This includes board and toll balancing exercises.
Postoperative phase 1 ( 1-5 weeks)
Possible examples of training knee self-mobility and quad and hamstring strength:
Week 1: Self-mobilization  Week 3: Strengthening exercises and gait training  Week 5: Strengthening exercises 
Week 10: Forward-backward and lateral power exercises  Week 12: Forward-backward and lateral power exercises  Week 15: Dash jump cuts 
- From now on, the progress of loading is the base.
- Proprioception and coordination exercises can be more specific to a patient’s individual motor needs. If the patient does not want to return to sports, these exercises can meet his ADL needs (climbing stairs uphill or downhill skating swimming…)
- Can include forward, backward and lateral dynamic movements as well as isokinetic exercises .
- After 3 months, patients can resume functional exercises such as running and jumping.
- Change directions more quickly as proprioceptive and coordination exercises become more intense. To stimulate coordination and control through afferent and efferent information processing exercises, it should be enhanced by altering the visible input surface stabilization (trampoline) speed Motor performance complexity, task resistance performance on one or two legs, etc. .
- The ultimate goal is to maximize the endurance and strength of the knee stabilizer, optimize neuromuscular control through plyometric exercises, and add exercise-specific exercises.
- Variations in acceleration and deceleration in running, turning and cutting movements improve joint motor reflexes to prevent new trauma during the race. 
Return to Sport
ACL injuries can lead to static and functional instability, leading to changes in movement patterns and increased risk of osteoarthropathy. In many cases, an ACL injury can lead to a premature end to a sports career. 
ACL Return to Sport: Hop Test|
Insufficient strength and explosiveness after surgery may be a risk factor for future injuries, and when athletes try to return to their previous performance levels, they may fail. A surgically repaired leg should have at least 90% better performance than your previously uninjured leg, researchers suggest Return to sports . The triple jump test can be used as part of a comprehensive physical and functional examination to help ensure not only a quick but also safe return to sports after ACL reconstruction. These 3 tests are sensitive enough to measure the left-right difference and can be used for A more advanced recovery phase after surgery to help ensure that the athlete’s exercise program successfully restores the injured leg to at least the level of the uninjured leg .
Athletes undergoing ACL reconstruction should be informed that postoperative participation in class I sports more than quadruples the 2-year knee reinjury rate. Later return to class I exercise and more symmetrical quadriceps strength before recovery significantly reduces this ratio .
As strength and fitness grow, the mechanisms of the previous injury can guide the final stages of rehabilitation: ACLR due to collateral injury mechanisms may focus on ankle-knee-hip coordination exercises or core stability or sport-specific posture .
Please see these pages for related return to sports
Open and Closed Kinetic Chain Exercises
Closed Kinetic Chain (CKC) and Open Kinetic Chain (OKC) exercises play an important role in restoring muscle (quadriceps hamstrings) strength and functional stability of the knee joint.
- In ACL rehabilitation, CKC exercises are more popular than OKC exercises. Some clinicians consider CKC exercises to be safer than OKC exercises because they place less stress on the ACL graft. In addition, they also believe that CKC exercises are more practical and equally effective as OKC practise. Bynum et al. (1995) concluded that the CKC exercise is safe and effective, but it sacrifices some important advantages compared to the OKC exercise. 
- A study comparing the amount of anterior tibial displacement in ACL-deficient knees during (1) anti-knee extension and OKC exercise and (2) parallel squat and CKC exercise concluded that ACL-deficient knees had significantly greater anterior tibial displacements. Displacement during extension The angle of knee extension is 64° to 10° compared to the parallel squat .
- However, in one study, no differences in the strain of the intact ACL were found between OKC and CKC exercises .
- Currently, ACL grafts may respond more like an intact ACL. Therefore, they believe that both types of exercise can be performed safely .
- However, a study examining the effects of OKC and CKC exercise on functional activity concluded that both OKC and CKC programs can lead to the same good long-term functional outcomes .
- In another study, group 1 used CKC only for quadriceps strengthening, while group 2 trained with CKC and OKC exercises starting at 6 weeks postoperatively  Knee stability was reduced at 6 months and also resulted in more athletes returning to previous activities earlier and maintaining the same level as before the injury. The authors concluded that a combination of OKC and CKC exercises is more effective than CKC exercises alone .
- Anterior knee pain is more likely to occur with an autologous bone-patella-tendon-bone graft than with an autologous hamstring graft. Therefore, the type of autograft can guide the physical therapist in choosing the correct period to insert the OKC sitting leg stretch. it will be earlier A case of a hamstring muscle transplant and a case of a patellar tendon transplant a few weeks later. Guidelines agree to insert OKC exercises within 4 weeks postoperatively .
- In any case, it is important to follow the progression of knee loading so as not to cause pain or laxity. A recent systematic review of randomized controlled trials comparing exercise for OKC versus CKC in patients after ACLR  found:
- No or insufficient evidence for differences in pain scores or joint laxity between OKC and CKC
- The former can be explained by (1) lack of sensitivity using the questionnaire (2) insufficient statistical power of the analysis or (3) practically no difference in pain experienced by patients undergoing OKC versus CKC
- There is weak evidence that open-chain exercises are better at improving knee extensor strength, as opposed to better active knee flexion in closed-chain exercises.
- No or insufficient evidence for differences in pain scores or joint laxity between OKC and CKC
- Non-weight bearing
- Motion that occurs at a single joint: isolated motion that promotes more shear forces 
- Distal segment free to move
- Resistance is usually applied to the distal segment
Chain Knee Extension Exercise
These exercises appear to have a controversial role in ACL rehabilitation programs, as several studies have shown that OKC stretch exercises from 60° to 0° flexion significantly increase tibial anterior translation and reconstructed ACL graft strain in ACL-deficient knees knee.  Despite these findings, OKC stretching exercises were not excluded from ACL rehabilitation programs, as the same study demonstrated that 90° to 60° flexion can be safely performed without increasing tibial anterior translation or ACL grafts The OKC Stretch strain. [twenty four]
In short, OKC stretches in an ACL rehabilitation program can be performed safely in ROM with 90° to 60° of flexion and are also useful for training isolated quadriceps.
Open Chain Knee Flexion Exercise
OKC flexion exercises play an important role in the rehabilitation process, as research shows no tibial anterior displacement or ACL graft strain during these exercises. Additionally, they cause isolated hamstring contractions. 
Closed-Kinetic-Chain Knee exercises
- Weight bearing
- Movements of multiple joints: compound movements that often create stress 
- The distal part is immobilized on a surface: the limb is in constant contact with the immobilization surface, usually the ground 
- Resistance can be applied proximally and distally: the entire limb is loaded .
Closed-Kinetic-Chain Knee exercises
CKC exercises play an important role in ACL rehabilitation because they cause hamstring-quadriceps co-contraction, which reduces tibiofemoral shear. In addition, studies have shown that body weight provides tibiofemoral compression while also reducing tibiofemoral shear during CKC exercises force. 
CKC exercises have several advantages over OKC exercises
- Increased knee stability (more joint compression)
- Functional load
- Strong coordinative training
- Minimal shear force
- Less stress on the ACL
- Training of the entire extension chain 
- No selective muscle training
- The weakest link in the chain is the one that feels the greatest overload and correspondingly the greatest training effect
- Fewer complications, such as patellofemoral symptoms
- CKC-exercises apply earlier than OKC-exercises
In a retrospective cross-sectional analysis by Culvenor et al . Patellofemoral pain (PFP) was present 12-15 months after ACLR with a hamstring graft in 30% of patients. People 27 and older were 2.6 times more likely to report PFP. Patellofemoral cartilage lesions menstrual tears (both As assessed by arthroscopy) pre-injury activity level time and gender from injury to surgery were not predictors of postoperative PFP.
Those with PFP did not experience a reduction in range of motion, but performed worse on jumping distance and single-leg tasks. Patients also reported significantly lower quality of life, poor exercise attitudes, and increased motor phobia.
PFP is important because maladaptive fear-avoidance movement patterns perpetuate pain and dysfunction by lowering the pain experience threshold. Appropriate language is recommended during rehabilitation and psychosocial interventions.