Patella Baja

Original Editor - Rishab Mishra Top Contributors - Rishab Mishra, Rishika Babburu and Vidya Acharya

Introduction

Patella baja, also referred to as Patella Infera, is a condition involving decreased patellar height. It is characterized by three features: a shortened patella tendon, a decreased distance between the inferior pole of the patella and the proximal articular surface of the tibia, and a distal position of the patella in the femoral trochlea.

Etiology

Patella baja is defined by an abnormally low position of the patella in relation to the femoral trochlea, typically resulting from a shortened patellar tendon or impairment of the knee’s extensor mechanism. This condition commonly develops following knee injuries or surgical interventions. Key contributing factors include extended periods of immobilization, excessive lowering of the patellar tendon during procedures such as tibial tubercle osteotomy or total knee arthroplasty (TKA), and insufficient post-surgical rehabilitation focused on restoring range of motion. Additional causes may involve the formation of scar tissue, adhesions, or inflammation impacting the patellar tendon and nearby tissues.

Pathophysiology

The pathophysiology includes quadriceps muscle weakness, extended periods of immobilization, and inflammatory responses that contribute to scarring and adhesions beneath the patella.

It commonly arises as a postoperative complication of knee surgeries such as total knee arthroplasty (TKA), anterior cruciate ligament (ACL) reconstruction, and tibial tubercle osteotomy.

Diagnosis and Indication

1. Severely Shortened and Nonfunctional Patellar Tendon:
   • Confirmed through clinical examination and lateral radiographs.
   • Often accompanied by significant functional impairment.
2. Increased Patellofemoral Joint Load:
   • Leads to pain and mechanical stress within the joint.
   • Typically occurs alongside reduced functional capacity.
3. Failure of Straight-Leg Raise Test:
   • Inability to perform a straight leg raise without extension sag.
   • Suggests compromised extensor mechanism requiring surgical intervention.
4. Medial and Lateral Restraints of the Extensor Mechanism:
   • Indicates tightness or fibrosis along the extensor pathway.
   • Reinforces the need for surgical correction.
5. Proximal Migration of the Patella (Over Time):
   • If the patella moves to a more functional position naturally but functional limitations persist (e.g., extension sag), patellar tendon reconstruction is indicated.

Rehabilitation

Immediate Postoperative Phase (Week 0–1):

• Flexion Limit: Restricted to the degree achieved intraoperatively without excessive tension on the repair (usually 80–90°).
• Brace: Use of a hinged knee brace locked in extension.
• Quadriceps Activation: Electrical stimulation applied to the quadriceps to promote early muscle engagement.
• Weight Bearing: Permitted as tolerated, with the brace locked in full extension.
• CPM (Continuous Passive Motion): Initiated on postoperative day 1, starting from 0° to 60° of flexion.

Early Phase (Weeks 2–6):

• Range of Motion (ROM): Gradually increased as tolerated, aiming to reach up to 90° by week 6.
• Physical Therapy Initiation: Begins at 2 weeks post-op, including:
  • Patellar mobilization in both medial and lateral directions.
  • Blood Flow Restriction (BFR) Therapy combined with quadriceps isometric exercises (quad sets)