Patella alta is a condition of the patella, or kneecap, whereby it rests in an abnormally high position in relation to the femur, or upper leg bone. Typically displacing a patella at one or one-and-a-half times its length out of place or more, this condition can result in pain and additional problems, such as patellar dislocation or subluxation, or traumatic failure of a supporting ligament. This affliction can occur genetically with an abnormally shaped trochlear sulcus, or femoral groove; or due to muscle imbalances, when tight muscles draw the patella upward in the femoral groove.
Non-invasive treatments may involve physiotherapy or the use of knee sleeves, braces, or tape. Additionally, medicines or arch supports can be used to train the movement and positioning of the patella. Common exercises may include stretching quadriceps and hip flexor muscles, as well as various leg exercises. Icing can relieve pain, which commonly may occur around the cartilage area behind the kneecap. Weight loss may also factor into treatment.
Misalignment of the patella aggravates the surrounding cartilage, causing blistering, fissuring, or wearing down. These conditions are referred to as chondromalacia patella. Causes include knee surgery or injury.
The condition of patella alta may be diagnosed using a lateral radiograph of the knee; this is essentially a side-view X-ray. Magnetic resonance imagers may be used but may not reflect an accurate portrayal of cartilage damage. An arthroscope can be inserted to transmit high-quality, illuminated digital video images in order to evaluate the positioning, cartilage wear, and situation of the bone and groove. Surgery is less often needed to treat the condition.
A common affliction, patella alta occurs in many people but does not always create problems. People may, however, be more likely to suffer knee dislocations, particularly if they contribute to the problem by taking up activities like running. This problem may be alleviated by switching to lower-impact activities, like biking. The opposite condition from patella alta is called patella baja, in which the kneecap rests too low.
Diagnosing the conditions of patella alta or baja requires an analysis of the Insall ratio, calculated as length of the patella against the length of the patellar tendon at a 30-degree angle. A 1:1 ratio occurs in healthy knees; a 20% variance will indicate either of the aforementioned conditions. One variation on this formula is the Insall-Salvati ratio, which eliminates angle of knee flexion from the equation.