John D. MacGillivray, M.D.: InjuryDetail: Patella Malalignment/Dislocation

Injuries and Conditions: Knee: Patella Malalignment/Dislocation: Medical Details

	Overview The knee cap (patella) acts as a fulcrum to lessen friction and provide efficient flexion and extension of the knee. A groove on the front of the thigh bone (femur) allows the kneecap to slide up and down while the joint is in motion. Some individuals have more shallow grooves in the thigh bone which may predispose them to dislocation injuries. Also, those individuals that have suffered repeated knee injuries or have abnormal anatomy of the knee may be at greater risk for dislocation. Young adults are prone to the injury because of increased flexibility (and ligamentous laxity) which allows joints to move more easily, sometimes allowing the knee to move into untoward positions. Young females are particularly at risk because of their limberness. This risk from increased flexibility is compounded by an increased Q angle (when the hips are much wider than the knees) and a sometime "knock kneed" gait while running or playing sports. This bent-in angle of the knee allows the kneecap to more easily move out of the femoral groove, making it more susceptible to dislocation.
	Causes of Injury A dislocated patella is typically the result of sudden changes in direction while running or jumping. Any force which causes the knee joint to rotate may displace the patella from its natural position. Injuries may also occur from a direct blow to the knee. In rare cases, the patella can dislocate after a powerful muscle contraction in which the patella is dislocated by the strong pull of the quadriceps (thigh) muscles. Patella dislocations are common in activities like basketball, soccer, and football which involve running, sudden turning and stopping.
	Diagnosis
	The initial dislocation commonly results in extreme pain. The dislocation is often visible, although the doctor will also check for additional injuries that may have occurred with the dislocation. A review of the patient's medical history will check for similar injuries in the past.

Anatomy

Product Considerations

Orthotics
An orthotic insert fits inside a shoe and helps position the foot in an anatomically correct position while walking, running, or jumping. Frequently, abnormal foot motion and gait occurs as a result of over-pronation of the foot; most orthotics are used to treat this condition. Over-pronation is a tendency to roll the foot onto the inner edge, loading the inside of the foot and leaving the outer edge almost weightless. A professionally made orthotic insert will exactly contour to the bottom of the foot, and can compensate for over-pronation or other abnormal foot mechanics.

One of two construction methods may be used to create an orthotic; one utilizes a plaster mold of the entire foot to make a moderately rigid insert, the other utilizes a foam impression of the bottom of the foot, creating a more flexible insert. In either case, the finished product must be tilted with small wedges, while other accommodations are made to protect sensitive areas of the foot. The choice of orthotics and design will vary according to the expected use, foot type, and body weight.

Orthotics can be used to treat:

abnormal foot mechanics

patella dislocation or maltracking

patellar tendonitis

general knee pain

ankle instability

Knee: Patellar Supports
Patella tracking supports are used to maintain the kneecap in its proper position while the knee is in motion. Patients that have a poorly tracking or misaligned kneecap will usually be directed to wear a support to prevent the kneecap from dislodging from the femural groove. Pressure applied by the support is adjustable, allowing changes to the support according to the condition of the knee. The support fits firmly around the knee with pressure to each side of the kneecap. Construction of the support is thin and elastic, which allows for easy movement and enables the support to be worn under loose fitting clothing.

Patella tracking supports can be used to treat:

Patellar malalignment

Patellar dislocation

Patellar instability

Anterior knee pain

Knee: Patellar Tendon Brace
Patellar Tendon Braces are designed to provide stress relief to the patellar tendon. Patellar tendonitis is an inflammation of the patellar tendon, usually at the insertion site where the patellar tendon attaches to the tibia. These braces apply pressure over the patellar tendon just above or proximal to the insertion site. By applying pressure above the area where the tendon attaches to the tibia, the end point for the tendon is changed. This new end point now bears the stress of the patellar tendon during activity. This allows the inflamed insertion site to rest.

Patellar Tendonitis is common among jumpers because of the stress that is applied to the tendon during this activity. Patients that have patellar tendonitis may be directed to wear a brace to allow the tendon to rest during activity. The role of a patellar tendon brace is to relieve the stress placed on the patellar tendon and its insertion site during activity.

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