By Dr. Mayank Daral (Olympic Certified Orthopedic Surgeon)

Undergoing Anterior Cruciate Ligament (ACL) reconstruction is a significant step toward returning to an active lifestyle. 

However, many patients believe the hard work ends once they leave the operating room. In reality, the first few weeks of post-operative care are critical in determining the long-term success of the surgery.

One of the most frequent questions I receive from patients is: Should I keep my knee straight or bent while resting?

While a bent knee might feel more comfortable, clinical evidence suggests that maintaining full knee extension (straightening the leg) is the single most important habit for a successful recovery.

The Danger of the Comfortable Bent Knee

After surgery, the body’s natural response to pain is to keep the joint in a slightly flexed (bent) position. Patients often place a pillow directly under the knee crease to relieve tension. As an orthopedic surgeon, I strongly advise against this.

Resting in a bent position for prolonged periods can lead to Arthrofibrosis—the formation of excessive scar tissue. This results in "extension loss," or a permanent inability to fully straighten the knee. Even a loss of 3–5 degrees of extension can lead to a limp, chronic anterior knee pain, and early-onset osteoarthritis.

ACL surgery recovery | Knee extension| Orthopedic surgeon
  • Prevents Contractures: Keeping the knee straight stretches the posterior capsule, preventing permanent stiffness.
  • Quadriceps Reactivation: To walk normally, your brain must be able to "fire" the quadriceps muscles. It is neurologically easier for the body to activate these muscles when the knee is in full extension.
  • Optimal Graft Healing: Proper alignment ensures that the new ACL graft is not subjected to abnormal stresses during the early healing phase.

The "Ankle Prop" Technique: A Surgeon’s Secret

  • The best way to ensure your knee stays straight without constant effort is to use the Ankle Prop.
  • The Method: While lying down, place a rolled-up towel or a firm small pillow strictly under your heel or ankle.
  • The Goal: There should be a visible gap between your knee and the bed.
  • The Result: This allows gravity to gently push the knee downward, encouraging full extension while you rest or sleep.

When is Bending Okay?

Bending the knee is essential for regaining range of motion, but it should be done through active exercises as prescribed by your surgeon. It should not be your primary resting position. If you must bend the knee for a break, do so only for short intervals (10–15 minutes) before returning to the extended position.

Specialist Consultation Suggested

A successful ACL recovery is a partnership between surgical precision and patient discipline. 

Small adjustments in your daily resting habits can be the difference between a return to elite sports and a lifetime of joint stiffness.

If you are experiencing persistent stiffness or have questions about your post-operative progress, always consult with your orthopedic specialist.

Dr. Mayank Daral (Olympic Certified Orthopedic Surgeon)

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