Over 200,000 anterior cruciate ligament (ACL) surgeries occur in the US every year.[1] The anterior cruciate ligament or ACL is one of the four major ligaments in your knee.[2] Other than a direct blow to the knee, injuries usually occur in sports that involve sudden movements such as a quick stop or changes in direction. Common sports that cause ACL injuries include but are not limited to soccer, American football, basketball and volleyball. ACL reconstruction surgery is a surgery that replaces a torn ACL.[2] The torn ligament is removed and replaced with a tendon; a band of tissue connecting muscle to bone. Regaining full knee straightening also called knee extension range of motion or ROM is one of the most important goals following an ACL surgery.[1] Many studies show that people are able to fully straighten their knee and that they have good outcomes after ACL surgery.[1] However, it doesn't mean that knee straightening is easy, which is why I want to help answer some common questions about knee straightening after ACL surgery.

When will I regain full knee straightening or knee extension?

The goal for full knee straightening or extension after an ACL reconstruction surgery is usually 8-12 weeks or between month 2 and 3 after your ACL surgery. For most people, the first four weeks are geared towards letting the tendon regrow and hypertrophy or get bigger and the following 4 weeks focus on strengthening the tendon.[4]

Timeline and Possible Recommended Exercises

Please use the following as a guide and understand that this is based on research-based ACL protocols but it may not be appropriate for you if you did not have a standard ACL surgery. Also, check with your health care provider to ensure these exercises are safe and appropriate for you. You can also learn about an overall ACL recovery timeline by reading our previous blog.

The suggested knee extension exercises listed below should be completed daily if you had a standard ACL surgery.

Immediately Postoperative ACL Surgery Week 0-1

Goal: Controlling pain, swelling and inflammation. Put weight on the surgical leg if cleared to do so by your surgeon.


Muscle setting exercises - contraction and relaxation of your leg muscles without moving the leg, just squeeze and relax your leg. These are also called isometric exercises.

Ankle pumps

Straight leg raises

Heel slides

Knee extensions or knee straightening. Typically in the 1st week you will not be able to fully straighten your knee. When your leg and knee are flat this is referred to as 0 degrees of knee extension. You will be lacking knee extension in the 1st week. Your knee may stay bent when you try to straighten it and this is normal in week 1. Typically people lack 10 to 20 degrees of knee extension and this is called "-10," "minus 10" or "-20," "minus 20" degrees of knee extension. The "-" or "minus" indicates that you have not yet acheived 0 degrees of knee extension.

Lying on your stomach and bending your knee unless you had a hamstring tendon graft for your ACL

Other tips: cryotherapy which is the use of ice or any other cold therapy, postsurgical compression wraps such as a tensor bandage, and elevation while using ice and compression.

ACL Surgery Week 2-3

Goal: full weight-bearing without crutches with a normal walking or gait pattern


Continue with the exercises from phase 1, can increase from -20 or -10 to 0 degrees of knee extension. It is hard in the 2nd and 3rd week but you should be working hard towards attaining 0 degrees of knee extension.

Gait training - walking on a treadmill or flat surface without crutches

Stationary Cycling and NOT outdoor cycling

Swimming typically from week 3 onwards as long as you have had your stitches removed and you scars are healing well.

ACL Surgery Week 4-6

Goal: Near full range of motion, double leg squats, single leg calf raises

0 degrees or knee extnesion

Stair stepping or climbing from week 4 onwards


Step ups - stand in front of a stair or step stool, place your foot on it, rise up shifting your weight onto the top leg and tighten your quadriceps muscles

Step downs - same process as step ups but start with your leg on the step and lower your body and leg down in a slow and controlled manner.

Calf raises

Hip extensions

Hamstring stretch

ACL surgery Week 7-8

Goal: Near full range of motion or full range of motion, full weight bearing with normal gait

0 degrees or more of knee extension. Many people have more than 0 degrees of knee extension. This means that your knee bends back more than a straight line which is normal. Extension that is greater than 0 is termed "plus" or "+" degrees of knee extension. If a person's knee bends 5 degrees more than a straight line this is termed "+5" or "plus 5" degrees of knee extension.


Continuation of exercises from phase 1 and weeks 4-6

Exercises where you are loading the surgical leg more and single leg exercises such as the step up, lunges and single leg sit to stand from a chair.

How can I improve my knee extension ROM after ACL surgery?

Loss of knee extension is a common complication after ACL reconstruction surgery.[5] Before your surgery, it is beneficial to know that being able to extend your knee fully decreases your likelihood of experiencing extension loss issues after your surgery. Extension loss can also lead to abnormal articular cartilage and poor quadriceps movement, these are the muscles at the front of your thigh, making it important to stick to your rehabilitation exercises.[5] Articular cartilage is the tissue that covers the ends of bones where joints form, allowing the joints to move more easily. Recommended treatment strategies to achieve full extension include exercises such as low load prolonged stretching and calf stretching.[1] There is often a weekly progression with knee extension rehabilitation. Progress in ROM should be monitored and continuously assessed to make sure you are reaching your knee extension goals based on your rehabilitation protocol and the advice from your healthcare provider.[4] You can also find some practical tips for improving your knee extension and knee flexion after ACL surgery by reading this blog.


ACL reconstruction surgeries are quite common and therefore the rehabilitation process and timeline is very well understood and researched. However, people often worry about their rehabilitation progress and specifically if they are achieving their knee range of motion at a normal rate. Sticking with or adhering to your rehabilitation protocols or programs is crucial in the success of regaining full knee extension. It is important to remember that not everyoneโ€™s timeline will be the same, but 8-12 weeks is the average time to regain full knee extension after an ACL surgery.

If you have had an ACL surgery and you want clear daily, weekly and monthly guidance for your knee extension as well as daily exercises for your recovery try our app Cuorvate. Curovate provides video-guided daily exercises, weekly goals for range of motion and exercises, progress tracking, the ability to measure your knee and hip range of motion and in-app chat with a physical therapist.

If you need further customized assistance during your ACL recovery check out our Virtual Physical Therapy page to book your 1-on-1 video session with a physical therapist.

Get it on Google Play

Other recommended blogs


1. Agarwalla, A., Puzzitiello, R. N., Liu, J. N., Cvetanovich, G. L., Gowd, A. K., Verma, N. N., Cole, B. J., & Forsythe, B. (2019). Timeline for Maximal Subjective Outcome Improvement After Anterior Cruciate Ligament Reconstruction. The American journal of sports medicine, 47(10), 2501โ€“2509.

2. Beck, P. R., Nho, S. J., Balin, J., Badrinath, S. K., Bush-Joseph, C. A., Bach, B. R., & Hayden, J. K. (2004). Postoperative pain management after anterior cruciate ligament reconstruction. The journal of knee surgery, 17(01), 18-23

3. Hill, G. N., & O'Leary, S. T. (2013). Anterior cruciate ligament reconstruction: the short-term recovery using the Knee Injury and Osteoarthritis Outcome Score (KOOS). Knee surgery, sports traumatology, arthroscopy : official journal of the ESSKA, 21(8), 1889โ€“1894.

4. Using the Pain Scale. (n.d.). Specialist Hospital Shreveport. Retrieved June 17, 2021, from

5. Ochiai, S., Hagino, T., Senga, S., Yamashita, T., Oda, K., & Haro, H. (2017). Injury to infrapatellar branch of saphenous nerve in anterior cruciate ligament reconstruction using vertical skin incision for hamstring harvesting: risk factors and the influence of treatment outcome. Journal of orthopaedic surgery and research, 12(1), 101.