How does the patella tendon heal following Bone-Patellar-Tendon (BPTB) Anterior Cruciate Ligament (ACL) reconstruction?

Patellar Tendon Healing Following BPTB ACL Reconstruction

The patellar tendon following bone-patellar tendon-bone (BPTB) ACL reconstruction undergoes a progressive healing process that requires careful rehabilitation to prevent complications while optimizing recovery. 1

Healing Process and Timeline

• The patellar tendon experiences reduced strain in all regions (medial, lateral, and central) during early recovery (<24 months post-surgery) compared to long-term recovery (≥24 months), with the central region (harvest site) showing the lowest strain regardless of recovery timeframe 2
• The medial and lateral regions of the patellar tendon demonstrate varying strain patterns based on time from surgery and effort level, suggesting differential healing rates across the tendon 2
• Healing progresses from an initial inflammatory phase to a remodeling phase, with most patients requiring at least 19 weeks of rehabilitation for adequate tendon healing 3

Rehabilitation Considerations to Support Healing

• Early mobilization is recommended as it can reduce patellofemoral pain in BPTB graft patients (from 35% to 8%) compared to patients who remain non-weight-bearing for 2 weeks 1
• Isometric quadriceps exercises including static quadriceps contractions and straight leg raises can be safely prescribed during the first 2 postoperative weeks to maintain muscle activation without excessive tendon strain 1
• Closed kinetic chain exercises can be safely initiated from week 2 postoperative to promote healing while minimizing stress on the donor site 1
• Open kinetic chain exercises should be introduced cautiously from 4 weeks postoperative in a restricted range of motion (90°-45°) with gradual progression to full ROM by week 8 1

Potential Complications During Healing

• Patellar tendon rupture is a rare but serious complication that can occur during rehabilitation, particularly during eccentric loading or maximum voluntary isometric contractions 4
• Partial tears of the patellar tendon may be managed non-operatively if extensor mechanism remains competent and there is no significant patella alta 5
• Excessive strain on the weakened patellar tendon during early rehabilitation can lead to anterior knee pain, which should be regularly monitored 1

Optimizing Healing Outcomes

• A 19-week rehabilitation protocol has shown no differences in knee laxity or other outcomes (strength, functional, proprioception, and subjective function) compared with longer duration protocols 3
• Both concentric and eccentric training improve quadriceps strength during the healing process without significant differences between training types 1
• A combination of eccentric and plyometric exercises is more effective in improving balance, functional activities, and subjective knee function than either training method alone 1
• Platelet-rich plasma (PRP) application to the donor site has shown promise in reducing subjective pain and potentially enhancing bone gap filling, though further research is needed 6

Rehabilitation Progression Based on Healing Timeline

• Weeks 0-4: Focus on early mobilization, isometric quadriceps exercises, and closed kinetic chain exercises to promote initial healing 1
• Weeks 4-8: Gradually introduce open kinetic chain exercises with progressive range of motion (90°-45° in week 4, progressing to full ROM by week 8) 1
• Weeks 8-19: Implement combined strengthening approaches including eccentric training and neuromuscular exercises to optimize tendon healing and functional outcomes 1
• Beyond 19 weeks: For return to pivoting/contact sports, aim for a Limb Symmetry Index (LSI) of 100% to ensure adequate healing and strength of the patellar tendon 1

Monitoring Healing Progress

• Regular assessment of anterior knee pain during rehabilitation is essential, as it may indicate excessive strain on the healing patellar tendon 1
• Varying knee joint angles and effort levels during rehabilitation exercises can target specific regions of the patellar tendon to promote optimal healing across all areas 2
• Accelerating quadriceps strengthening in a controlled manner may enhance strain distribution across the patellar tendon to promote more effective healing 2