ACL Tears

There are approximately 100,000 to 200,000 ACL ruptures per year in the United States alone. These injuries are common in professional and recreational athletes across multiple different sports. ACL injury may place that athlete at risk for developing arthritis in the future. The majority of athletes elect to undergo ACL reconstruction (ACLR) secondary to their goal to maintain the ability to engage in athletic endeavors, however, others choose non-operative care.

About 50% of those who suffer ACL injury also sustain an addition injury to their meniscus, cartilage or other ligaments about the knee. A thorough work-up is crucial to ensure the extent of injury sustained.

ACL injury is more common females (~4-5 to 1), and females often sustain ACL injuries at a younger age. Research has taught us that jump-landing mechanics have a role in causing ACL injuries, particularly in young, adolescent athletes. At present time, ACL injury prevention programs focus on neuromuscular training and plyometric activities – which we perform via our COSMO Fit Lab – to address landing mechanics and uncover muscle weakness and imbalances.


ACL Anatomy + Function

The ACL provides the majority of the knee’s effort to prevent anterior (forward) translation of the tibia relative to the femur. The ACL also acts as a secondary restraint to rotation of the tibia and varus/valgus stress. The ACL is essential to knee stability, ensuring the tibia does not rotate internally about the femur. At the time of injury, the athlete is often planting their foot and pivoting or twisting; this injury is commonly non-contact in nature. The knee partially dislocates, which results in the pathognomonic bone bruising seen on MRI.

Physical Examination + Work-Up

Individuals may describe an audible “pop” at the time of injury, then immediate onset of pain, swelling and difficulty with weight bearing. Not everyone has this dramatic of a presentation, others have more vague symptoms of pain, swelling and a feeling of mild instability with pivoting and twisting. On exam, we assess your range of motion (how much you can bend and extend), the symmetry of your ligaments in a side to side comparison of both knees, including a Lachman test.

Lachman Test:

This clinical test is used to evaluate the integrity of the ACL. With the knee bent to 30 degrees of flexion, the femur is stabilized while the examiner applies an anterior directed force to the tibia. If the knee is ACL-deficient, the tibia will move forward in relation to the femur excessively.

Varus and Valgus Stress Test:

This clinical test is used to evaluate the integrity of the lateral collateral ligament (LCL) and medial collateral ligament (MCL), respectively. The knee is held in 20 degrees of flexion and loaded in varus or valgus distally such that the LCL or MCL is placed on stretch. The examiner assesses the amount of opening/gapping at the lateral (varus) and medial (valgus) joint space. The test is repeated with the knee in full extension.

Pivot Shift Test:

This clinical test is used to evaluate for an ACL rupture. It may be difficult to perform in clinic due to pain/muscular guarding; however, it may be performed in the operating room under anesthesia. With the patient lying on their back, the affected knee is fully extended with the tibia internally rotated. The examiner then applies a coupled valgus and internal rotation force while flexing the knee. An appreciable “clunk” is felt at approximately 30 degrees of knee flexion if the ACL is torn.


X-rays are evaluated for alignment, the presence of degenerative changes at the joint, for fracture or an avulsion injury. MRI is also performed to assess the integrity of the ACL and for additional injuries to the meniscus, cartilage and ligaments, such as the MCL, LCL or PCL (posterior cruciate ligament).

ACL Surgery

The torn ACL is reconstructed with a new ACL graft. Both ACL surgical technique and graft selection have undergone immense research in the orthopaedic surgery literature. Many factors including age, activity level, sex and patient interests influence the graft choice. Dr. Logan and Dr. White use both patellar tendon and quadriceps autograft (the patient’s own tissue) techniques during ACL reconstruction surgery. The final graft choice is based on a discussion between our physicians and the patient. Allografts may be considered in patients of certain age and activity groups.

ACL Reconstruction Rehabilitation

Following ACL reconstruction (ACLR), an individualized, criterion based physical therapy rehab progression is essential to optimizing outcome.

The general principles of post-operative ACLR rehabilitation programs have undergone dramatic change over the past few decades. While athletes once followed time-based progression protocols, the tide has shifted to criterion-based protocols. These newer guidelines allow phase advancement only when the athlete demonstrates successful completion of the phase and its goals.

The initial goal tasked to an athlete following ACLR is to attain full symmetrical knee range of motion, particularly full extension. Early activation of the quadriceps is also important; however, full motion is essential before more advanced strengthening may commence.

Early quadriceps strengthening focuses on muscular endurance, followed by more aggressive strengthening, then power and agility. Sport-specific exercises are incorporated only after full strength and control are demonstrated.

Neuromuscular training may be implemented into the rehabilitation program early on; however, the chosen exercises must fall within the overall phase goal (endurance, strengthening, power/agility, etc).

The determination of readiness to return to sport is multi-factorial and the treating therapist must consider both physical and psychological readiness. The final chapter of this eBook will outline our recommendations to assist the athlete in the safe and successful return to play.

Early Recovery 0-6 weeks

Range Of Motion

Immediately following ACLR, the primary emphasis is on edema control and range of motion, particularly full extension. Loss of extension results in abnormal joint arthrokinematics, leading to abnormal articular contact pressures. Full extension is achieved through both hands-on (manual therapy) and active exercise (quadriceps sets). Athletes should avoid resting with a pillow under their knee, as this works against achievement of full extension

Further, both therapist and patient-directed patellofemoral joint (PFJ) mobilizations assist with obtaining full extension and may begin as early as postoperative day (POD) #1. Flexion ROM to 120 degrees or greater should be met by 4 weeks, with full, painless, symmetric ROM to contralateral extremity achieved by 3 months. Both manual and active/active-assist exercise should be employed, including supine wall slides, stationary bicycling and seated active-assist knee bends.


Immediate brace settings are influenced by multiple factors and athlete-specific parameters should be confirmed with the surgeon. For example, a brace may be locked in full extension to protect a meniscus or meniscus root repair or following a concurrent cartilage procedure. A post-operative brace Is often initially locked at 0° for ambulation to protect the harvest site or to protect the patient who has received a regional (femoral or adductor) nerve block. The brace is opened when quadriceps control is demonstrated via a strong straight leg raise with a lag.
We recommend patients sleep in their post-operative brace, locked in zero degrees of extension to help avoid the development of a flexion contracture.

Weight Bearing Status + Gait

Weight bearing status following ACLR is dictated by graft selection, surgeon preference and the presence or absence of concurrent procedures (such as, meniscal repair). Progression to weight bearing as tolerated may be immediate, with discontinuation of crutch use with the patient can demonstrate ambulation without a limp.

Quadriceps Control

The return of quadriceps control will assist in establishing proper gait and set the proper foundation for forthcoming therapeutic exercise progression. Measures to control post-operative effusions, such as ice, elevation and compression, will help the return of quadriceps control and reduce quadriceps inhibition.

Quad setting throughout the day during the early post-operative period will encourage quadriceps control. While patients should not relay on electrical simulation units, NMES can be used as an adjunctive therapy to quadriceps sets to facilitate a better contraction. Some patients also respond well to the combination as a means to facilitate their understanding of the goal of quadriceps setting.

When this criterion is met, the post-operative brace can be opened to allow normal knee range of motion during ambulation. Crutches are continued at this point until a non-antalgic gait is demonstrated.

Muscular Endurance: Week 7-12

Closed kinetic chain exercises including leg press and squats inside a pain free arc of motion are introduced as these activities have been shown to minimize stress to the ACL. Rehab professionals should assist the patient in maintaining full ROM, safely progress strengthening, and promote proper movement patterns. The protocol should not advance if post-exercise pain and swelling is evident. Further, one should avoid activities which induce pain at the graft donor site (such as kneeling).

Muscular Strength: Week 12 to 18

Throughout this progression, the rehab clinician should closely monitor the patellofemoral joint for crepitus and complaints of pain. Do not advance through the programming if pain or swelling is present.
A running program may be initiated. We recommend beginning with aqua jogging, followed by land training on flat surfaces. Once short-mileage is achieved, then consider advance distance and terrain (hills/slope), but only add one variable at a time. Speed is the last variable to be incorporated.

Muscular Power + Agility: Week 19 to 24

Plyometric training is then incorporated only if the patient exhibits full, painless ROM in addition to proficient strength with the preceding exercises.
Plyometric training progressives in a stepwise fashion with regard to speed, load, volume, and frequency of exercise, all while ensuring quality of movement. Single-plane movements progress to multi-plane movement, as well.

High-Level Activities: Week 25+

When to return to sport following ACLR is a hot topic within the sports medicine world. Time-based progression and return to sport have fallen out of favor, and clinicians now understand the importance of developing testing criterion to inform this decision. Surgeons and rehabilitation professionals must work together to utilize multiple forms of assessment, both clinical and psychological.

Available measures include subjective rating scales, physical examination, isokinetic testing, functional testing, balance testing, and qualitative movement assessment (such as with quality of movement with landing). In addition to employing multiple assessments, clinicians must have realistic expectations about the differences between clinical testing and on-field play, as the pressure and excitement of game time play may lead to altered quality of movement and technique.

ACL Injury Prevention at COSMO Fit Lab

While ACL tears are common, much of the medical literature has been dedicated to efforts to reduce the incidence of this injury.

The medical literature has found multiple risk factors for ACL injury, which include:

  • Extrinsic Factors (playing surface and conditions)
  • Genetic Factors (familial predisposition, collagen polymorphisms)\
  • Anatomic Factors (tibial slope, notch width)
  • Hormonal Factors
  • Biomechanical & Neuromuscular Factors (landing and jumping techniques and strength)
  • While some risk factors are “non-modifiable,” neuromuscular training can be employed as an effective tool in the prevention of ACL injury.

Our on-site assessment includes the Biomotion Analysis and a Functional Movement Screening. Testing is performed within the COSMO Fit Lab within our clinic in Denver, CO.

Biomotion Analysis with a sensorless system, enabling calculation of joint angle during common functional movements, such as squatting and jumping. In comparison to the majority of products available on the market, our system uses no infrared technology but utilizes image-based techniques. High quality video recordings with high frame rates and high resolutions are captured and saved using synchronized industrial cameras.

Functional Movement System Screening to evaluate for strength, flexibility and movement quality deficits, as well as recognize movement patterns that support sport-specific activities. This data enables us to prescribe individualized exercise recommendations to correct the body asymmetries we know are a risk factor for injury.

After this comprehensive assessment is performed, an Individualized Needs Assessment is provided by one of our hand-selected physical therapist partners with our training recommendations. Our preferred Partners have been hand-selected due to their expertise in injury prevention, performance and rehabilitation.

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