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Q Angle

The Q angle, or quadriceps angle, is often measured when a physician is examining and evaluating a patient for knee pain. This angle is an important indicator of the biomechanical forces that act on the knee.

Measurement

The Q angle is formed between two lines representing pulling forces on the knee. The first line is the longitudinal axis of the femur (thigh bone), which represents the line of pull of the quadriceps muscles on the knee. This line is created by measuring from the center of the patella (kneecap) to the anterior-superior iliac spine of the pelvis. The second line represents the pull of the patellar tendon on the kneecap. Measuring from the center of the patella to the tibial tubercle creates this line (see Figure 1). The normal Q angle values are 17° in females and 14° in males. Women naturally have a larger Q angle than men because women tend to have wider pelvises than men. Other causes for increased Q angle include knock-knees (genu valgum), femoral anteversion, and other slightly abnormal alignment of the legs.

Problems Associated with a Large Q Angle

A larger-than-normal Q angle is associated with a disorder called abnormal quadriceps pull. In a patient with a large Q angle, the kneecap will be pulled sideways when the quadriceps muscle contracts. This increases the biomechanical stress on the knee during strenuous or repetitive activities and thus increases the likelihood of knee pain and injury. The abnormal pull of the quadriceps on the patella can also cause abnormal tracking of the patella in the femoral groove (the normal “track” in which the patella moves). The pain associated with this abnormal tracking is called patellofemoral pain syndrome. An increased Q angle also places a patient at increased risk for chondromalacia of the knee, patellar subluxation, and anterior cruciate ligament injuries.

Figure 1 The Q Angle

None
Note: The Q angle is an important indicator of the biomechanical forces acting on the knee.

Treatment

The goal of treatment is to decrease an abnormally large Q angle. One of the most effective ways to achieve this goal is to use custom-made, flexible orthotics. These shoe inserts are designed to help reduce stress on the knee.

  • knees
  • patella
  • pain
Katherine StabenowDahab
http://dx.doi.org/10.4135/9781412961165.n415
See also

Further Readings

CrocettiiM., & BaroneM.A., eds. Oski's Essential Pediatrics.
2nd ed.
Philadelphia, PA: Lippincott Williams & Wilkins; 2004: 682–683.
KuhnD.R., YochumT.R., CherryA.R., & RodgersS.S.Immediate changes in the quadriceps femoris angle after insertion of an orthotic deviceJ Manipulative Physiol Ther257465–4702002http://dx.doi.org/10.1067/mmt.2002.127171
LoudonJ.K., JenkinsW., & LoudonK.L.The relationship between static posture and ACL injury in female athletesJ Orthop Sports Phys Ther24291–971996
MageeD.J.Orthopedic Physical Assessment. Philadelphia, PA: WB Saunders; 1987: 296.
TomsichD.A., NitzA.J., ThrelkeldA.J., & ShapiroR.Patellofemoral alignment: reliabilityJ Orthop Sports Phys Ther233200–2081996
WheelessC.R., ed. Wheeless’ Textbook of Orthopaedics. http://www.wheelessonline.com
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