Physical Examination for Patellofemoral Instability

We use 2 patient cases to demonstrate relevant physical examination findings when evaluating patients with patellofemoral instability.

Case 1 is a 19-year-old female college soccer player with multiple recurrent instability events. Case 2 is a young man in the military service, who is also 19 years old, who began having recurrent instability after a hard landing while skydiving.

Normal patellar glide is 2 quadrants laterally and 1 quadrant medially; greater than 3 laterally indicates hypermobility. The moving apprehension test is performed with stepwise flexion to determine when the patellar engages the trochlea and no longer shifts laterally. It is important to ensure the quadriceps is relaxed. This test can help distinguish patellar instability from pain-related buckling. The jumping J sign is seen when the patella is completely disengaged from any bony restraint when going from flexion to extension of the knee.

On physical examination, both patients had positive effusion, tenderness, apprehension, and patellar tilt. Case 1 had an apprehension test positive to 80° of flexion, patellar mobility with a 2-quadrant shift laterally, and a soft J-sign. Case 2 instability was more prominent on examination with a moving apprehension test to 90°, a 4-quadrant shift laterally, and the prominent jumping "J" sign.

The physical examination, in addition to imaging, is essential for operative planning. For case 1, we proceeded with right knee tibial tubercle osteotomy, medial patellofemoral ligament reconstruction, lateral retinacular lengthening, and loose body removal. For case 2, we proceeded with right knee trochleoplasty, tibial tubercle osteotomy, medial patellofemoral ligament reconstruction, and lateral retinacular release.

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