The tibiofemoral joint is comprised of the convex femur and concave tibia which move along a coronal axis during flexion and extension. Internal rotation occurs in a transverse plane and abduction and adduction occur in a coronal plane. Within the knee are four main stabilizing ligaments: MCL, ACL, LCL and PCL.

external image anatomy.jpg

MCL: runs from the medial femoral condyle to the anteromedial surface of the tibial condyle. This ligament controls valgus movements of the knee.
ACL: attaches from the anterior intercondylar area on the tibia, runs posterior, superior and laterally to attach on the medial side of the lateral femoral condyle. The bands of the ACL are taut throughout knee ROM thought the greatest resistance is seen with hyperextension. This ligmanet limits interal rotation of the tibia.
LCL: originates at the lateral condyle of the femur and inserts at the posterior/ inferior border of the fibular head. This ligament controls varus force at the knee.
PCL: attaches at the posterior intercondylar area of the tibia, then runs superior or anterior and medially to the anterior medial femoral condyle. This ligament also has two bands. The anteromedial is taut with flexion and the posterior lateral is taut in extension. Together these bands limit internal rotaion of the tibia.

Other important structures of the knee include:
  • Patellar tendon (patella to tibial tubercle)
  • Arcuate ligament (head of fibula to femoral condyle)
  • Arcuate complex (includes arcuate ligament, LCL, popliteus, and the lateral gastroc head)
  • Oblique popliteal ligament (connects posterior femoral condylse then blends into semimembranosus, reinforces the lateral capsule and limits tibial anteromeidal rotation)
  • Posterior oblique ligament (posterior to MCL)

Menisci also exist within the knee to provide cushioning for the joint. The menisci can be broken into two components, medial and lateral.
  • Medial menisci: attach to the articulating surface of the tibial plateau, the deep surface of the knee joint capsule and intercondylar fossa. This portion of the meniscus is c-shaped and thicker in the posterior portion than in the anterior portion.
  • Lateral mensici: attach at the tibial plateau, deep surface of knee joint and intercondylar fossa as well. However, this portion of the meniscus is O-shaped and equal in thickness anteriorly and posteriorly but thickened along the peripheral borders.

Mechanism of Injury

  • Deceleration Injury
  • Most are non-contact
  • Pivot or twist on a planted foot
  • Landing or cutting activities
  • Knee hyperflexion or hyperextension (end ranges of motion)
  • Valgus force at the knee during sports (contact force to the lateral aspect of the knee)


Typically depends on the severity of the tear:
  • Grade 1: 25% or less is torn= No visible injury
  • Grade 2: 25-75% of ligament is torn= Marked swelling and tenderness
    • Pain and swelling may come a few hours after injury
  • Grade 3: greater than 75% is torn= Gross swelling and antalgic (painful) gait
    • Rapid pain and swelling occur immediately after injury and will worsen during the first 4 hours

Patients often recall a "popping" or "giving out" during time of injury. These are attributed to the tibia sublaxing anteriorly. Other signs and symptoms include bruising, warmth, intermittent generalized ache, pain, immediate dysfunction, local tenderness, knee instability, and inability to walk without assistance.

+ Tests: Lachman's Test, Anterior Drawer, Shift Pivot Test

Classic Signs:
  • Hemarthrosis (blood into a joint or synovial cavity) causes pain, edema, and joint stiffness
  • Atrophy of quadriceps

Behavior of Symptoms:
Aggravating: prolonged weight bearing, pivoting, going up or down stairs
Alleviating: rest



Time to recover varies depending upon the surgeon or doctor's protocol and upon each individual patient. Most protocols outline that the patient should be able to return to sport or activity around 3 to 4 months post surgery, assuming that they have met the required criteria put down by their surgeon. A 6 month and 12 month follow up is generally recommended by the physician as well for ligament laxity testing and functional testing.

An example of the time frame and different phases of a protocol are:
Post-op Day 1 - 7
Immediate Post-op protection
Weeks 2-3
Maximum Protection Phase
Weeks 4-7
Controlled Ambulation Phase
Weeks 7-12
Moderate Protection Phase
Months 2.5-3.5
Light Activity Phase
Months 3.5-4.5
Return to Activity Phase


The article, Rehabilitation of patients following autogenic-bone patellar tendon-bone ACL reconstruction: A 20 year perspective, explains the development of ACL rehabilitation over 20 years. It talks about the evolution of ACL rehabilitation, using evidence based practice, from non-accelerated to accelerated. The article explains the Methodist Sports Medicine Center's accelerated protocol in detail with numerous articles supporting its framework. In summary, many clinics have tried to replicate this protocol and continue to use it as a framework for accelerated ACL rehabilitation.

Methodist Sports Medicine Center Accelerated Rehabilitation Program (summarized):

Phase I: Preoperative (strong evidence for delayed surgery with preoperative rehab)
Goals - reduce swelling and restore motion and gait prior to surgery
Exercises - ROM, heel slides, heel props, prone hangs, squats, step-downs

Phase II: Early Postoperative
Goals - control swelling**, gain full extension, get PROM flexion to 110 degrees, establish good quadricep control
Exercises - heel prop, quad sets, SLR. Gait training and mini squats towards the end.
Cryotherapy (evidence shows decreased use of medication)
Used CPM set at 110 degrees for flexion at beginning
Evidence showed immediate weight bearing improves recovery with no adverse effects of ligament laxity later on.

Phase III: Intermediate Postop (3-4 weeks)
Strengthening initiated gradually as long as ROM met
High rep, low intensity exercises
Closed chain exercises initiated: step downs, mini squats (evidence for better protection of ACL repair compared to OKC. Also evidence for the use of both with caution of OKC)
KT-1000 ligament arthrometer tests

Phase IV: Advanced Rehabilitation (5-8weeks)
Goal: increase strength and initiate early sport activities
Exercises: light agility drills, proprioceptive activities (progression)
at end of 8 weeks - KT- 1000 test performed
Evidence for early sport activity at 5.1 weeks (no compromise to graft)

Phase V: Return to Activity
Goals: Individualized to patient
Progression of exercises
Typically returned to full activity in 4-6months
Evidence for excellent long-term results (5 years and 15 years follow ups) for accelerated rehabilitation (97% normal radiographs)


Here is a PDF file of an ACL protocol The University of Kentucky Sports Physical Therapy
Below is a link to The Institute for Arthroscopy & Sports Medicine in San Francisco's ACL reconstruction protocol, where Dr. Jeffrey Halbrecht is the Medical Director.

Here is a PDF file to an article containing an eccentric exercise program for ACL repairs



NWB vs WB Exercise

Non-weight bearing vs Weight bearing
Wilk and colleagues mention in their article the differences between tensile forces and loading on the injured ACL with NWB and WB exercises. While both can be beneficial, it is important to understand which exercises put a high torque on the joint when designing the exercise intervention. Here is a table that summarizes some of their findings, with the exercise that strains the ACL the most listed first:

Rehabilitation Exercise (Peak Strain at Knee Angle)
Isometric Leg Extension (seated)
30 Nm Torque
4.4% at 15°
Dynamic Leg Extension (seated)
10 lb resistance
3.8% at 10°
Lachman Test
150 N (33 lb)
3.7% at 30°
Squatting (with or without)
136 N (36 lb) of resistance
3.6% - 4.0% at 10°
Dynamic leg extension (seated)
No external resistance
2.8% at 10°
Single-leg sit-to-stand
Tested at 30°, 50°, and 70°
2.8% at 30°
Step-up/-down and stair climbing
Tested at 30°, 50°, and 70°
2.5% - 2.7% at 30°
Leg press
40% body weight resistance
2.1% at 20°
Forward lunge
Tested at 30°, 50°, and 70°
1.9% at 30°
Stationary bicycling


Most ACL strain occurs during knee flexion angles of 0-30 degrees, and as you can see in the table above there is more stress on the ACL with a non-resisted seated leg extension than there is with closed chain exercises such as squats (even with resistance). Another way to decrease strain on the ACL is to change the trunk position. This can be done by performing squats and lunges with a more forward trunk tilt. This will help recruit the hamstrings and will unload the ACL by decreasing anterior tibial translation. ACL strain can also be decreased in these exercises by making sure the knee does not translate anteriorly beyond the toes.

Things to think about:
-If adding resistance, position the resistance nearer to the knee rather than around the ankle
-The hamstring musculature parallels the tibial plateau at 90 degrees flexion. Seated flexion at these angles is an appropriate early exercise for patellar grafts but may but too much load on the hamstrings immediately in those with a hamstring graft
-Squatting with a vertical trunk position can load the ACL- this causes the center of mass to be posterior and in order for it to move anteriorly the knees come in front of the toes.
-Take caution when initiating rapid deceleration with plyometric drills
-Addition of external resistance does not appear to increase ACL loading with WBing exercise
-Controlling knee valgus with females (front step-downs, lateral step-downs with resistance, squats with resistance around distal femur)

Full Extension

The most common reason for poor outcomes following ACL reconstruction is failing to regain full extension range of motion. Inability to gain full extension can cause an increase in patellofemoral contact pressure, increased scar adhesion in the anterior aspect of the knee and poor movement quality. There are several ways to increase extension motion, including PROM, supine heel props, and gastroc stretching. Two additional methods are pictured below:

Top: weight is applied proximal to patella for long load low duration stress. Should apply 5-10 lbs of overpressure a couple times a day for 12-15 minutes for best outcomes. Bottom: extension machine applying pressure above patella to regain motion

Other Exercises

(from article by Manske, et al.)
  • Early Execises:
    • Heel slides as tolerated
    • Wall slides 0-45 degrees (for hamstring repairs)
    • Patellar mobilizations
    • Quad sets (with NMES if poor control)
    • Gastrocnemius/Hamstring stretches (NWBing)
    • Multi-hip exercises
    • Quadriceps isometrics at 60 and 90 degrees
    • Toe raises bilaterally (watch WBing status)
    • Terminal knee extension with theraband
    • Balance (weight shifting bilaterally once they can WB as tolerated)
    • Bike for ROM
  • Exercise options weeks 4-6:
    • Wall slides 0-90 degrees
    • Toe raises unilaterally
    • Leg press bilaterally
    • Balance- begin unilateral
    • Hamstring curls
    • Flexibility as appropriate
    • Initiate step-ups in pain-free range
  • Advanced Exercises
    • Advanced Closed Kinetic chain: single leg squats, leg press unilaterally
    • In-line jogging
    • Bilateral plyometric exercises
    • Progress proprioception
    • Walk/jog progression
    • Single leg cone pick-up (maintain knee alignment)
    • Tibiofemoral mobilizations if joint limitations

Assistive Devices


A physician may order a brace to be worn when ambulating during the first 1-3 weeks post-op. The brace provides stability and is usually locked in full extension and gradually flexed to 90 degrees depending on the patient's swelling, quad strength, and functional stability.


Crutches are typically used during 1-2 weeks post-op with weight bearing as tolerated and can be discontinued when normal gait is achieved.



Important for controlling swelling post-op. It should be applied for 20-30 minutes at least 3-4 times daily.
The Game Ready is a portable system that combines controlled intermittent compression and cold therapy. There are specific wrap sleeves designed for the knee joint and others. See Game Ready video for ACL: http://www.gameready.com/view/kneebound.html


Interferential Current Therapy:
The effects of IFC of decreasing pain post-op have been examined in randomized, double blinded studies. Evidence shows that IFC is effective at reducing pain and swelling 24 hours after surgery up to 9 weeks. This also assists in gaining more ROM during PT and additionally decreass the amount of pain medication the patient is taking. Thus, resulting in an overall quicker return to ADLs and athletic activities.


Neuromuscular Electrical Stimulation:
Inhibition of the quadriceps muscle post-surgery is a problem due to the existence of pain and swelling after injury. It has been concluded in the literature that the use of electrical stimulation combined with exercise was more efficient than exercise alone in improving quadriceps strength post-ACL injury. Patients should be encouraged to actively contract the quadriceps when using NMES, and NMES should be discontinued once the patient can independently contract the quadriceps.

external image Jon_ACL_photo1.jpg

Alternative Treatments

If you google ACL treatments, one of the first websites you will come across is www.mendmyknee.com

This website claims that there are 3 things that professional athletes use to mend their knees in order to return to full recovery: ultrasound, a cold compression wrap and a deep knee inferno wrap to promote blood flow. They instruct patients to apply these things 3-4 times a day for optimal healing and claim that is all you need for a full recovery. I think it is important to remind your patient that while these things are important, gaining full motion and strengthening the knee are needed for returning to optimal function and preventing reinjury, and that these should only be an adjunct to therapy.


The APTA has a website through their MoveForward campaign where you can look up many different symptoms and conditions and see how a physical therapist can help. This website also contains a great document of exercises to perform in order to try to prevent an ACL injury.

This website also states that researchers have made the following recommendations for a preventive exercise program:
  • The program should be designed to improve balance, strength, and sports performance.
  • Strengthening you core (abdominal) muscles is key to preventing injury, in addition to strengthening your thigh and leg muscles.
  • Exercises should be done 2 or 3 times per week and should include sport-specific exercises.
  • The program should last no fewer than 6 weeks.

The article, Anterior Cruciate Ligament Injury: Diagnosis, Management, and Prevention from the American Family Physician Journal talks about a study that was performed that investigated the use of this prevention program on 5,000 female soccer players ages 14 to 18 during two athletic seasons. From those who participated in this program, only two experienced ACL tears. From the control group, 32 players experienced ACL tears. This article also stated that a meta-analysis of ACL prevention protocols showed that plyometrics, strength training, and balance exercises combined with regular feedback associated with proper positioning while landing are the most important exercises for ACL injury prevention.


Prevent Injury, Enhance Performance Program

Warm-up (50 yards each)
Jog line to line

Shuttle run (side to side)

Backward running
Stretching (30 seconds per stretch, two repetitions per stretch)
Calf stretch
Quadriceps stretch
“Figure four” hamstring stretch
Inner thigh stretch
Hip flexor stretch
Walking lunges (20 yards for two sets)

Russian hamstring (10 repetitions for three sets)

Single toe raises (30 repetitions on each side)
Plyometrics* (20 repetitions each)
Lateral hops over 2- to 6-inch cones

Forward/backward hops over 2- to 6-inch cones

Single leg hops over 2- to 6-inch cones

Vertical jumps with headers

Scissors jump
Shuttle run with forward/backward running (40 yards)

Diagonal runs (40 yards)

Bounding run (50 yards)
Research by Moksnes et al (2008) evaluated whether screening tests which are used to determine if a patient requires ACL reconstruction are effective. One hundred twenty five subjects were included in the study and those who passed the hop tests and were determined to be "copers" following the ACL injury. Copers were described as subjects who were able to return to previous athletic activites after the ACL using conservative treatment and not surgical repair. In a one year follow up these copers were found to be performing previous athletic activites in 65% of cases. These subjects were deemed true copers while the non copers included subjects who were still limited following conservative treatment and would have benefitted from surgery. Overall, the findings were that there are no great screening tools to determine if ACL patients will recover with conservative treatment or if surgery is the best option.


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