Patellofemoral Instability FAQs

What does patella do?

Patella acts as a fulcrum to transfer the load of contraction of the quadriceps to the leg and redirecting it. It helps in improving the efficiency of the function of quadriceps tendon.

Is it normal for kneecaps to move?

There is a normal amount of excursion of the kneecap from side to side in the groove of the lower end of femur. This allows proper functioning and range of motion of the knee joint.

Is patellar subluxation genetic?

Patellar subluxation can be genetic due to the laxity of the ligaments or problems with the axis of the leg. Patellar subluxation may also be caused due to multiple trauma causing injury to the ligament.

What is patellar instability?

Patellar instability means that the kneecap is not sitting well into its groove on the lower end of the thigh bone or the femur. The patella tends to ride on the outer aspect of the groove and causes pain and swelling. These patients may have damage to the cartilage. Occasionally the patient may have frank episodes of instability when the kneecap dislocates to the outside of the groove, will present with acute onset of pain and swelling.

The kneecap can be reduced back but the patient may have had injury to the cartilage as well as the ligament on the inner side of the knee. Some patients may have inherited factors that may cause patellar instability. If the patient has recurrent instability or damage to the cartilage and ligament, then these patients may need surgery to improve their function as well as prevent long-term effects of patellar instability.

How long does it take to recover from a dislocated kneecap?

Usually after first time dislocation of the kneecap without complications in the form of injury to the cartilage or ligament, the patients may recover over a span of six to eight weeks with the use of brace, anti-inflammatory medications and physical therapy.

What causes kneecap to dislocate?

Kneecap can be dislocated due to trauma, accident or fall. Occasionally the patients may be predisposed to the dislocation of the kneecap due to bony abnormalities and may cause their kneecap to dislocate with very subtle trauma or injury.

How do you measure the Q angle?

The Q angle is usually measured by looking at the axis of the thigh bone to the leg bone. This measurement helps in knowing if the patient has predisposition to patellar instability. If the patient has very high Q angle which can be collaborated with clinical and radiological findings, then they may need to undergo surgical correction to decrease the Q angle and prevent patellar instability and pain and prevent long-term complications in the form of early degeneration of the patellofemoral cartilage.

What is trochlear dysplasia?

Trochlea is the groove on the lower end of thigh bone in which the patella sits and glide. Occasional the patient’s trochlea may not be well-developed in the form of good groove so that the patella does not sit in and is unstable. These patients are said to be having trochlear dysplasia.

What is patellar realignment surgery?

Patellar realignment surgery is usually done by osteotomy of the tibial tubercle in which the bone is cut and replaced to decrease the Q angle and align the patella into the groove. This helps in preventing long-term complications of accelerated degeneration of the patellar cartilage.

What do you do in a MPFL reconstruction?

MPFL or the medial patellofemoral ligament is a restrain from allowing the patella to dislocate towards the outside of the knee joint. It can be torn in patients with patellar dislocations and may need repair or reconstruction if the patient has recurrent instability. During reconstruction a tendon graft is used to stabilize the patella to the inside of the femur using sutures and anchors.

What is genu valgum deformity?

Genu valgum deformity means that the alignment of the leg to the thigh bone is excessively towards the outwards. These patients may also present with knock-knee in which the inside of the knee rubs each other while standing or walking. These patients have increased stress over the outer side of the knee as well as on the patellofemoral joint. If the patients are symptomatic and not improved with conservative means, then surgical treatment of genu valgum may be required to prevent long-term effects of early degeneration of the cartilage.

What is a J-sign of the knee?

A J-sign of the knee is usually found in patients of patella alta in which the patella is high riding. These patients may have multiple joint ligamentous laxity also.