A 66-year-old woman who underwent posterior-stabilized total knee arthroplasty 2 years ago reports a painful audible clunk during active knee extension from 30 degrees to full extension. Examination shows crepitus over the anterior knee but no effusion and stable implants. The most likely cause is:
- A Loosening of the femoral component
- B Entrapment of a fibrous nodule formed at the superior patellar tendon origin within the intercondylar notch of the femoral cam housing ✓
- C Wear-through of the tibial polyethylene post
- D Patellar component dissociation
Correct answer: B. Entrapment of a fibrous nodule formed at the superior patellar tendon origin within the intercondylar notch of the femoral cam housing
Explanation
Patellar clunk syndrome is specific to posterior-stabilized knees. A fibrosynovial nodule develops at the junction of the quadriceps tendon and suprapatellar pouch and catches against the anterior edge of the femoral intercondylar box as the patella engages the trochlea in terminal extension. Treatment is arthroscopic debridement of the nodule. Implant stability and component fixation are unaffected, which excludes loosening and polyethylene wear as causes here.
Reference: Miller's Review of Orthopaedics, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.