Strengthening the Quadriceps After ACL Reconstruction

Weak quadriceps after ACL reconstruction often hamper patients’ ability to return to sport and to function in everyday life. At a national meeting of the American Physical Therapy Association, physical therapists were reporting that this problem is widespread, even two years after surgery.

Patients at Shelbourne Knee Center routinely regain quadriceps strength, return to sport, and regain normal knee function. Eight-five to 90% of the high school and college athletes we treat return to sport, compared to 50-60% nationally. (1)

Physical therapists Bill Claussen, PT, and Scot Bauman, PT, DPT, decided to gather data about the rehab program to show how our patients achieve these results. “We wanted to share what works well in our practice so other practices can apply this and improve their results,” says Claussen, who is the rehab supervisor at Shelbourne Knee Center.

Study of 217 ACL Reconstruction Patients

Claussen and Bauman conducted a retrospective study of 217 Shelbourne Knee Center patients who underwent primary ACL reconstruction using a patellar tendon graft (PTG) from the contralateral knee between 2009 and 2013.

Before surgery, physical therapists measured bilateral range of motion (ROM) and strength. Values for the non-involved knee became the baseline normal values.

After ACL reconstruction, rehab goals were divided between the knees:

  • ACL knee: Restore full extension followed by flexion
  • Donor knee: Restore tendon strength through low-load, high-repetition exercise.

Physical therapists recorded:

  • Bilateral strength and ROM at 1, 2, 3, and 6 months and 1 year postoperatively
  • International Knee Documentation Committee (IKDC) data for normal ROM in the ACL knee compared to the opposite knee.

High Levels of ROM and Quadriceps Strength

Claussen and Bauman reported these results (2):

  • The percentage of patients who achieved full extension in the ACL knee was 98% at 1 month post-op and 100% at 1 year post-op
  • The percentage of patients who achieved full flexion in the ACL knee was:
    • 17% at 1 month post-op
    • 85% at 6 months post-op
    • 94% at 1 year post-op.
  • At 1 year post-op, 94% of patients achieved both normal extension and flexion compared to the opposite knee.

Quadriceps strength in both knees also returned. Compared to preoperative baseline values, patients achieved quadriceps strength:

  • ACL knee:
    • 91% at 6 months post-op
    • 101% at 1 year post-op
  • Donor knee:
    • 84% at 6 months post-op
    • 95% at 1 year post-op.

Claussen and Bauman reported their findings in the poster session at the 2018 Indiana American Physical Therapy Association and Kentucky American Physical Therapy Association Joint Conference, held in September 2018 in Louisville, Ky.

Return to Sport and Normal Function

“It is possible to get ACL knee strength back in the first year after surgery and to pass return-to-sport criteria and achieve normal function,” says Claussen.

Key elements in Shelbourne Knee Center ACL rehab model are:

  • Restoring ROM prior to strengthening
  • Using a contralateral PTG, which provides a predictable return to normal strength in both knees.

A Rehab Model for the Field

“The model we utilize may be a viable way for people who are struggling with post ACL reconstruction results to improve them,” says Claussen.

He also notes that the current trend to delay return to sport to avoid re-injury is unnecessary and not founded in data. “If the knees are in good shape, the likelihood of re-injury is independent of when the patient returns to sport.”

For more information about ACL rehabilitation, please call 888-FIX-KNEE.


  1. Czuppon S, et al. Variables associated with return to sport following anterior cruciate ligament reconstruction: A systematic review. Br J Sports Med. 2011;48:356-364.
  2. Claussen W, Bauman S. Return of bilateral quadriceps muscle strength following anterior cruciate ligament reconstruction using a contralateral patellar tendon graft, presentation at 2018 Indiana American Physical Therapy Association and Kentucky American Physical Therapy Association Joint Conference, September 2018.