Exercises / Thigh & knee

Seated knee extension (open chain)

Strength
Thigh & knee
Ankle weight or leg extension machine

Isolated quadriceps loading. Range can be limited (90°-45°) to reduce patellofemoral stress and ACL graft strain early.

Also called leg extension, OKC knee extension, knee extension machine.

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Where you stand

No published distribution for this exercise yet. We add one only from a peer-reviewed study.

Muscles worked

Filled: primary.

How much

Typical strength dose: 2-3 sets of 8-12 repetitions at a load that is hard by the last repetition, 2-3 days per week (ACSM novice guideline). Adjust to symptoms.

Start: Sitting

Steps

Sit with the knee bent to 90°.
Straighten the knee against resistance through the prescribed range.
Lower slowly.

Cues

Controlled tempo
Stay in the prescribed range

Common mistakes

Swinging
Using the hip to lift

Used for

Quadriceps weakness after ACL reconstruction (restricted range early)
Patellofemoral pain (90°-45°)

Take care (1)

After ACL reconstruction, follow guideline timing and range restrictions for open-chain work.

Evidence (2)

Knee extension with variable resistance through 90°-45° limits patellofemoral joint stress.1
Open kinetic chain quadriceps exercise can be used after ACL reconstruction within restricted range and timing.3

Easier

Straight leg raise

References (3)

Powers CM, Ho KY, Chen YJ, Souza RB, Farrokhi S. J Orthop Sports Phys Ther. 2014;44(5):320-327. Patellofemoral joint stress during weight-bearing and non-weight-bearing quadriceps exercises
Neumann DA. Elsevier. Kinesiology of the Musculoskeletal System: Foundations for Rehabilitation. 3rd ed.
van Melick N, van Cingel REH, Brooijmans F, et al. Br J Sports Med. 2016;50(24):1506-1515. Evidence-based clinical practice update: practice guidelines for anterior cruciate ligament rehabilitation based on a systematic review and multidisciplinary consensus