Patellar Tendon Strength Recovery After BPTB ACL Reconstruction
The patellar tendon does return to normal functional strength after bone-patellar tendon-bone (BPTB) anterior cruciate ligament (ACL) reconstruction, though this occurs through compensatory enlargement of the cross-sectional area rather than restoration of the original tissue quality. 1
Healing Process and Timeline
- The patellar tendon undergoes a compensatory enlargement of approximately 21% in cross-sectional area (CSA) compared to the uninjured side, which enables recovery of tendon stiffness 1
- While the Young's modulus (material quality) remains approximately 24% lower than the uninjured side, the increased CSA allows for functional recovery of tendon strength 1
- Most patients require at least 19 weeks of rehabilitation for adequate tendon healing according to clinical guidelines 2
- A 19-week rehabilitation protocol shows no differences in outcomes compared to longer protocols (32 weeks) in terms of knee laxity, strength, and function 3
Rehabilitation Considerations for Optimal 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 2
- Isometric quadriceps exercises including static quadriceps contractions and straight leg raises can be safely prescribed during the first 2 postoperative weeks 3
- Closed kinetic chain exercises can be safely performed from week 2 postoperative 2
- Open kinetic chain exercises should be started cautiously from 4 weeks postoperative in a restricted range of motion (90°-45°) 2
- Gradual progression of range of motion is recommended: 90°-30° in week 5,90°-20° in week 6,90°-10° in week 7, and full ROM by week 8 2
Potential Complications During Rehabilitation
- Open kinetic chain exercises might induce more anterior knee pain compared with closed kinetic chain exercises in BPTB graft patients 3
- There is risk of patellar fracture during rehabilitation, particularly during eccentric quadriceps exercises or maximum voluntary isometric contractions in the early rehabilitation phase (6-10 weeks postoperatively) 4
- Partial ruptures of the patellar tendon can occur but may be treated nonoperatively if there is no extensor mechanism incompetence or significant patella alta 5
Long-term Outcomes and Return to Function
- Both concentric and eccentric training improve quadriceps strength without significant differences between training types 2
- A combination of eccentric and plyometric exercises is more effective in improving balance, functional activities, and subjective knee function than either training method alone 2
- Approximately 65% of patients after ACL reconstruction return to preinjury competitive sport level within 2 years, but only 38% remain at the same level beyond 2 years 3
- Men are 1.4 times more likely to return to their preinjury sport level than women 3
- For return to pivoting/contact sports, a Limb Symmetry Index (LSI) of 100% is recommended to ensure adequate healing and strength of the patellar tendon 2
Monitoring During Rehabilitation
- Regular assessment of anterior knee pain during rehabilitation is essential, as it may indicate excessive strain on the healing patellar tendon 2
- Limb Symmetry Index (LSI) testing shows that only 23% of patients achieve >90% symmetry in leg muscle power and hop performance at 2 years after ACL reconstruction 3
- Neuromuscular training should be added to strength training to optimize outcomes and prevent reinjuries 2