What is a normal TT-TG distance?

Several studies suggest that a normal TT-TG distance is 10 mm or less [5, 7, 8]. A TT-TG distance greater than 15 mm in patients with patellofemoral insta- bility may predict limited benefit from phys- ical therapy [7].

What is an abnormal TT TG distance?

Tibial tubercle–trochlear groove distance There is a degree of variability in the literature about what is considered an abnormally high TT-TG. TT-TG distance of more than 20 mm is believed to be nearly always associated with patellar instability [27].

Is surgery necessary for dislocated patella?

Surgery is usually only necessary if there was a fracture or another associated injury, such as a ligament tear. It may also be done if you have dislocated your kneecap at least once before.

How can I improve my patella stability?

Nonsurgical treatment may include rest, regular stretching and strengthening exercises, taping or bracing the knee, using ice, and short-term use of nonsteroidal anti-inflammatory drugs (NSAIDs). Quadriceps strengthening is the most commonly prescribed treatment for patellar tracking disorder.

How is patellar translation ( TT-TG ) distance calculated?

Patellar translation (TT-TG distance) is an analysis performed by overlapping or superimposing axial images of the femoral condyles and tibial tuberosity. The measurements are used to quantify patellar instability.

How is patellar translation of trochlear groove measured?

Patellar translation can be measured using the tibial-tuberosity to trochlear groove distance (TT-TG distance) by calculating the transverse length between the trochlear groove on the femoral and tibial tuberosity on axial images. The measurements are used to quantify patellar instability.

Where is the TG line in the patella?

A line (see the red lines) could be drawn on the slice at the back of the rounded bits of the femur ( the posterior condylar line), and a second line could drawn perpendicularly from the deepest part of the groove under the patella (trochlear groove) to meet the other. The vertical line would be the TG line, since TG means ‘trochlear groove’.

How big is the TT-TG in patellar dislocation?

Using MRI in a recent series of cases, Dr. Sherbondy and Ashley Anderson, MD, Penn State sports medicine orthopaedics fellow, found average TT-TG distances of 12-13 mm in patients with repeated patellar dislocation (n=30), compared to 9-10 mm in normal controls without dislocation (n=38) (Figure).