What is the cause and treatment of a palpable mass in the patella tendon after Bone-Patellar-Tendon-Bone (BPTB) Anterior Cruciate Ligament (ACL) reconstruction?

Management of Palpable Mass in Patella Tendon After BPTB ACL Reconstruction

A palpable mass in the patella tendon after Bone-Patellar-Tendon-Bone (BPTB) ACL reconstruction is most likely scar tissue formation at the donor site and typically requires only conservative management with monitoring rather than surgical intervention.

Causes of Palpable Mass After BPTB ACL Reconstruction

• The palpable "ball" in the patella tendon following BPTB ACL reconstruction is commonly due to scar tissue formation at the harvest site where the middle third of the patella tendon was removed for the graft 1
• Other potential causes include:
  • Partial tear or disruption of the remaining patella tendon fibers 2
  • Inflammatory response at the donor site 1
  • Tendinopathy of the remaining patella tendon tissue 3

Assessment Approach

• Physical examination should focus on:

  • Location and size of the mass 2
  • Presence of pain with palpation or during activities 4
  • Assessment of extensor mechanism function (ability to perform straight leg raise, presence of extension lag) 2
  • Evaluation of patella height and tracking 2

• If the mass is painful or increasing in size, imaging may be warranted:

  • MRI can help differentiate between scar tissue, partial tear, or tendinopathy 3
  • Ultrasound may be useful for dynamic assessment of tendon integrity 1

Treatment Recommendations

Conservative Management (First-Line)

• Most palpable masses in the patella tendon after BPTB ACL reconstruction can be managed conservatively 2:
  • Activity modification to avoid excessive loading of the extensor mechanism 5
  • Gradual strengthening of the quadriceps with careful progression 6
  • Monitoring for any changes in size, pain, or function 1

Rehabilitation Considerations

• Balance quadriceps strengthening with protection of the donor site 5:

  • Begin with isometric quadriceps exercises that can be safely prescribed during early rehabilitation 6
  • Progress to closed kinetic chain exercises before open kinetic chain exercises 6
  • Avoid aggressive eccentric loading of the patella tendon in early rehabilitation 5

• The American Academy of Orthopaedic Surgeons (AAOS) guidelines recognize that BPTB autografts may increase anterior or kneeling pain compared to hamstring grafts 6, 1

When to Consider Further Intervention

• Surgical intervention is rarely needed but may be considered if 7:
  • Complete rupture of the patella tendon occurs 7
  • Progressive increase in patella alta (high-riding patella) 2
  • Significant extensor mechanism dysfunction 2

Prevention and Monitoring

• During rehabilitation following ACL reconstruction using BPTB autograft, clinicians should balance:

  • Improving quadriceps strength while protecting the donor site 5
  • Minimizing patellofemoral pain 4
  • Protecting the healing graft 5

• Rehabilitation protocols should include specific protection strategies for the donor site 1

• Patients should be educated about the normal healing process and expected timeline for resolution of the palpable mass 6

Prognosis

• Most patients with a palpable mass in the patella tendon after BPTB ACL reconstruction have good outcomes with conservative management 2
• The mass typically becomes less noticeable over time as scar tissue remodels 1
• Anterior knee pain is more common after BPTB grafts compared to hamstring grafts but typically improves with time 4