Why Is This Important?

Stiffness after ACL reconstruction surgery is a known complication. While most patients recover good movement with rehabilitation, some experience difficulty fully straightening (extending) or bending (flexing) the knee. This stiffness can limit walking, sports, and daily activities, so early recognition and proper treatment are important.

Why Does Stiffness Happen?

Stiffness after ACL surgery can occur for several reasons:

• Incorrect graft placement
  • If the reconstructed ACL is not placed in the correct position, it may block the knee from fully straightening.
• Inadequate physiotherapy
  • Recovery requires consistent and guided physiotherapy.
  • If the patient does not receive the correct rehabilitation or does not fully comply, the knee may become tight and lose motion.
• Cyclops lesion (scar tissue formation)
  • Extra inflammatory tissue can form at the front of the knee joint.
  • This scar tissue physically blocks the knee from extending fully.
• Other contributing factors
  • Swelling and pain after surgery can make patients reluctant to move the knee.
  • Individual healing differences (e.g., more scar tissue formation) also play a role.

Symptoms to Watch For

• Inability to fully straighten the leg.
• Inability to bend the knee to normal range.
• Pain, tightness, or a “block” sensation in the knee.
• Limping or difficulty walking normally.

How Is Stiffness Treated?

Physiotherapy (First-Line Treatment)

• Goal: Restore movement through stretching and strengthening.
• Patients work on:
  • Fully straightening (extension) exercises.
  • Fully bending (flexion) exercises.
  • Muscle strengthening and mobility drills.
• Commitment is key daily exercises and regular physiotherapy sessions are critical for success.

Manipulation Under Anesthesia (MUA)

• If physiotherapy does not improve stiffness, the surgeon may recommend an MUA.
• The patient is given anesthesia, and the surgeon carefully bends and straightens the knee without the patient feeling pain.
• This helps to break down adhesions (scar tissue) and improve range of motion.

Arthroscopic Debridement and Release

• If MUA is not successful, an arthroscopic procedure may be performed.
• Using a camera and instruments through small keyhole incisions, the surgeon:
  • Removes the cyclops lesion (scar tissue).
  • Releases tight tissues around the knee.
• This may restore movement, but results can vary.

Risks and Limitations

• Even with treatment, persistent stiffness can remain in some patients.
• As with all surgery, there are risks including:
  • Infection.
  • Persistent stiffness despite treatment.
  • Rare complications from anesthesia or surgical intervention.

Preventing Stiffness After ACL Surgery

• Start physiotherapy early after surgery, as advised by your surgeon.
• Focus on extension first regaining full straightening is especially important.
• Stay consistent with rehabilitation exercises, even when uncomfortable.
• Control swelling and pain with ice, elevation, and medication so you can move the knee more easily.

Key Takeaway

Stiffness is a possible complication after ACL surgery, but with early physiotherapy, close follow-up, and timely interventions such as manipulation or arthroscopic release, most patients can regain good knee function. The best results come from active participation in rehabilitation and regular communication with your healthcare team.

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