REDUCED PATELLAR DISLOCATION

Typical constellation of signs Report should note: • Lateral condylar impaction microfracture • Medial retropatellar microfracture • Tear of MPFL •

Ant retropatellar cartilage shear injury • Carefully look for inferolateral femoral condyle shear osteochondral fracture Patellar length Patellar tendon length

PTR= PTL/PL Ratio of TTTG/PL also important

PATELLAR TRACKING

Tracking technique: • knees are supported on a foam cushion in approximately 30° of flexion. • Quadriceps loading is achieved by placing weights, using dedicated devices or decompressing an inflatable ball. • a series of fast gradient echo sequences are obtained • TR of 11 ms, a TE

of 4.2 ms and a 15° flip angle. • Seven 5 mm slices, six axial and one sagittal, are acquired in approx 8 s • The axial slices are positioned to include the full proximal excursion of the patella as the knee extends. T • This sequence is repeated 15 times giving a total imaging time of 2 min. •

Select the axial slice closest to the centre of the patella in each of the 15 sequences • Compile these into a cine-loop Various patterns of maltracking have been described. A subjective grading is:

• 1, minor perceptible lateral deviation or tilt; • 2, obvious lateral deviation or tilt; and • 3, gross patellar subluxation. As it subluxes, there is also a tendency for the patella to tilt laterally, presumably due to a rotatory force induced by quadriceps contraction