Squat, Press, Extend or Flex for Strong Legs & Healthy Knees, Pt. 6

In the conclusion of this series, we will look at some of the pros and cons of the movements that have been highlighted in this article.

There is always a risk to benefit ratio with all exercises. Over the last 10 years since we started to hear the whispers of the “better for your knee” exercise selections, here is what I have found:

For the argument presented, when we think of the shear compared to compressive forces applied to the knee when performing a leg extension versus a squat, leg press or lunge, it is clear that the better of the exercises are going to be the squat, leg press and lunges. Needless to say, the squat, leg press or the lunge can easily become worse exercises than the leg extension if performed in the incorrect manner. It is up to the fitness professional to coach a client and know how to progress or regress a movement. As a simple summary, the following chart illustrates the pros and cons of the movements that have been mentioned in this article.

Knee Extension vs. Squat, Leg Press, Lunge (SLL’s): Pros & Cons:

Knee Extension Pros Knee Extension Cons SLL’s Pros SLL’s Cons
Allows for the beginning stages of rehab in supervised controlled ROM settings. Puts a tremendous amount of shear forces on the knee. Shear forces are harder on the knee than compressive forces, as seen in SLL’s. Puts compressive forces on the knee, which are the type most accommodating to knee structures. Sometimes a client or patient cannot support their own weight due to a deconditioned state, surgery or handicap and cannot perform SLL’s.
Can be used with lightweight for a warm up or finishing movement after the heavily loaded movements are performed. Can’t build muscle size. Muscle size requires maximum stabilization with compound movements to lift max weight. You cannot lift max weight for muscle size using a single-joint movement. Allows for max weight to be used when seeking size in the lower body due to the compound muscle actions occurring at the hip, knee and ankle simultaneously.
Some have reported increased stress on the rectus femoris which becomes something a bodybuilder may want to focus on for aesthetic purposes. Isolates the quadriceps. Employs co-contraction/relaxation of all lower body muscle groups during the entire performance, therefore builds muscle uniformly.
Does not mimic any ADL’s and very few sports (dysfunctional for human movement performance). They mimic ADL’s and Sport (functional for human movement performance).
Does not allow for sufficient energy depletion. Client will not receive the benefits of being able to burn much fat with a single joint movement when compared to multi joint movements Allows for maximum energy depletion due to the compound muscle groups working together. The fat loss client will benefit greatly from this.

The Recommendations

Beginner/No reported knee problem/Can perform basic ADL’s unassisted

  • Teach the squat from the most basic progressions
    • Bodyweight sit-to-stand/stand-to-sit using bench or chair
    • Bodyweight sit-to-stand/stand-to-sit without a bench or chair
    • Lateral resistance walks
    • Medial resistance walks
    • Assisted single leg squats using a bench
    • Non-assisted single leg squats using a bench
    • Stationary non-alternating supported lunge
    • Stationary non-alternating unsupported lunge
    • Bilateral leg press
    • Unilateral leg press
    • Use the leg curl machine to strengthen the hamstring

Severely Deconditioned/No reported knee problem/Needs assistance with ADL’s

  • Use the leg extension as a mobility tool
    • Will strengthen the leg muscles but at a much lower % than CKCE’s
    • Will increase blood flow to area
    • Eventually work on sit and stands as tolerated (squats)
    • Work the hip adductors and abductors or use the leg curl machine to strengthen the hamstrings

Severely Deconditioned/Reported knee problem/Needs or doesn’t need assistance with ADL’s

  • Use all modalities of the beginner with no reported pathology

General Fitness Client or Athlete with no knee issues

  • Teach the squat from the most basic progressions
    • Bodyweight sit-to-stand/stand-to-sit without a bench or chair
    • Lateral resistance walks
    • Medial resistance walks
    • Unassisted single leg squats using a bench
    • Stationary non-alternating unsupported lunges
    • Stationary alternating unsupported lunges
    • Walking lunges forward
    • Walking lunges backwards
    • Bilateral leg press or unilateral leg press
    • Bent knee deadlifts
    • Standing toe raises
    • Use the leg curl machine to strengthen the hamstring
    • Agility drills: Easy-to-Moderate for general fitness difficult for an athlete

General Fitness Client or Athlete post rehab

The following guidelines were confirmed and are used by the office of Al DeSimone, South Florida Institute of Sports Medicine in Weston, FL. Per Paul Buchanan, PA-C at the South Florida Institute of Sports Medicine, the ACL is the most common of the general fitness and athletic injuries. The suggested practice for a patient cleared for exercise in a post-rehab setting is a series of the following protocols:

  • Perform all Closed Kinetic Chain Exercises, first and foremost.
  • Keep all movements linear verses lateral.
  • Avoid pivoting, cutting or ballistic accelerations and decelerations.
  • Implement sport- or skill-specific agility as tolerated by the client after going through the above progressions.


After reviewing all the available published and unpublished data, and speaking with and consulting with many fitness professionals, the following conclusions can be easily made:

CKCE’s rule over OKCE’s.

Do OKCE’s increase leg strength? Yes, they do. But when you look at the numbers, the percent values are so far apart that we have to really reconsider using leg extensions and leg curls to build size, strength and speed if the client can perform CKCE’s with no contraindications.

In a study by Fiatorone in 1990 that evaluated increases in strength in the lower body, it was shown that OKCE’s will increase strength. After 8 weeks of training, the CKCE group had increased strength by 175%, while the OKCE group increased only 48%. Nevertheless, an increase was seen which in part does justify the use of the leg extension. However, the risk of shear forces being higher and eventually causing excessive cartilage breakdown outweighs not being able to work the legs at all for the person who cannot perform CKCE’s.

For those that are able and want to keep their knees safer for the long run, we can conclude that sticking to CKCE’s is the way to go for maximum knee safety and functionality.


1. Collado H., Fredericson M., Patellofemoral pain syndrome. Clin Sports Med. 2010:29:379-398

2. De Cardo M, Armstrong B. Rehabilitation of the knee following sports injury. Clin Sports Med. 2010:29:81-106

3. Steiner T., Parker RD., Patella subluxation and dislocation. DeLee and Dree’s Orthopaedic Sports Medicine 3rd ed.

4. Clark, J. M. (1990). “The organization of collagen fibrils in the superficial zones of articular cartilage.” J Anat 171: 117-30.

5. Mechanics of human joints: Physiology, Pathophysiology, and treatment. Unsworth, A. 1993

6. Basic Orthopaedic Biomechanics, Second Edition, Van C. Mow, Wilson C. Haynes, 1997

7. Medial Collateral Ligament Tears, Cedars-Sinai, 2012, a 501(c)(3)

8. Arthroscopic repair of traumatic longitudinal meniscal tears, K Roeddecker, G.D. Giebel, C. Lohscheidt and M. Nagelschmidt, 1993, Vol 7 Num 1

9. Meniscus tear recovery time, Benjamin Wedro, MD, FACEP, FAAEM, 2012

10. Bursitis, The Basics, What you should know about bursitis, 2012 Carol Eustice, ASCP, ARHP

About the Author

Felix Doval is the founder and owner of Pro-Active Wellness, a leading South Florida Health and Fitness education provider whose curriculums are taught using the private training facilities of Active Bodyz Fitness Training located in Davie, FL. Felix holds a Master Certification with the NFPT, and is NSCA and NAHF certified.


These resources are for the purpose of personal trainer growth and development through Continuing Education which advances the knowledge of fitness professionals. This article is written for NFPT Certified Personal Trainers to receive Continuing Education Credit (CEC). Please contact NFPT at 800.729.6378 or [email protected] with questions or for more information.
Get 35% off certification packages

Celebrating 35 years

We’re celebrating 35 years with 35% off!

Our biggest discount EVER!

Get 35% off certification packages.