Patella Alta and Baja

Patella alta or high-riding patella refers to an abnormally high patella in relation to the femur. The patella sits high on the femur where the groove is very shallow. Here, the sides of the femoral groove provide only a small barrier to keep the high-riding patella in place. This condition has been associated clinically with patellofemoral dysfunction and is considered a predisposing factor for the development of patellofemoral pain (PFP)

Patella alta can occur as the result of a sports injury, though, it's largely majority of the time it is a congenital/developmental condition that is unrelated to trauma. Its pathophysiology is not completely clear, but it is hypothesized that one of the causes of patella alta, are abnormally long patellar tendons

Clinically Relevant Anatomy

The patella is a flat, inverted triangular bone, situated on the front of the knee joint. The patellofemoral joint is the portion of the knee joint between the patella and the femoral condyles. The patellofemoral articulation totally depends on the function of which are connected to the patella with a shared tendon. The quadriceps femoris is divided into four different muscles with the same insertion on the patella: the rectus femoris (RF), the vastus lateralis (VL), the vastus intermedius (VI) and the vastus medialis (VM). There is also a tendon that connects the bottom of the patella to the tibia, called the patellar tendon. This tendon is extremely strong and allows the quadriceps muscle group to straighten the leg. These three bones are covered in articular cartilage which is an extremely hard, smooth substance designed to decrease the friction forces. The patella lies in an indentation of the femur known as the intercondylar groove.

CLINICAL PRESENTATION

If the patella is sitting too high then this can cause two main problems:-

• Patellar instability.
• Increased contact pressures on the articular surface of the patella.

A common symptom of patellar injury and dislocation is acute pain after direct contact or sudden change of direction. With sudden changes in direction, the femur medially rotates over the ground-stabilized tibia. Under these conditions, athletes commonly feel the knee giving way, which is the result of quadriceps inhibition from pain, a physiologic protective mechanism. Rapid swelling, intense knee pain, and difficulty with any knee flexion usually occur. Other dysfunctions with similar presentations and mechanism of injury are meniscal and ligamentous injuries, particularly injuries of the anterior cruciate ligament.

Symptoms may also manifest as a slowly progressive sensation of anterior knee pain with increased physical activity. Such activities include inclined ambulation, squatting, prolonged sitting, and going up and down stairs. Anterior knee pain aggravated by activity is typical of chondral pathology. Knee pain that improves during physical activity but returns after activity suggests tendinitis.

Diagnostic Procedures

Patella alta is mostly defined with imaging-based measurements and rarely by description. Imaging includes lateral radiographs, sagittal MRI, radiographic ratios measured on MRI, and patellar tendon length.

Examination

The patient sits on the edge of the examination table with the feet on the ground. The knees are bent at 90 degrees, and the thigh is horizontally positioned. The vertical position of the patella height is best observed from lateral. In Patella Alta it can be seen that the partially tilted patella protrudes above the level of the thigh. This is more remarkable in a unilateral Patella alta. A patella alta may be noticed during inspection. The knee has two striking bulges: one is the tibial tuberosity, the other one is the patella. The space distal to the patella and proximal to the fat body of Hoffa is characterized by a notch.

Physical Examination

The second diagnostic step is a careful, complete and essential physical examination. The purpose of this examination is to reproduce the symptoms (pain/instability) and to locate the painful zone. The location can indicate which structure is injured; it is truly helpful to compose the diagnosis and to plan the treatment.

Medical Management

Tibial tuberosity osteotomy can be performed in patients with patella alta. With this surgery they move the attachment of the patellar ligament downwards to the tibia. The patella is also attached to this ligament, so the patella moves downwards. The quadriceps angle can be increased with patella alta, this can be corrected by shifting the bony attachment of the patellar ligament inwards.

A couple things that may occur after the surgery is done are infection, stiffness of knee joint, nerve injury and recurrent instability. The patient has to use crutches to walk after the surgery is done. This will affect the movement of the knee, this is why physical therapy and exercise should be done after surgery in order to get rid of the pain and swelling. Muscle control will also increase with physical therapy. The recovery period should be around 3-6 months.

Physical Therapy Management

Non-operative treatment for a high riding patella will include:

• Rest: from aggravating activities to allow any inflammation to settle
• Physical Therapy: Manual therapy can help to improve the resting position of the kneecap. Manual gliding is performed to theoretically modify the resting height of the patella before knee extension, resulting in decreased pain in the knee. Correction of the positional fault of the patella by using tape, is a method to correct patellar alignment
• Strengthening Exercises: strengthening the knee, kneecap and buttock muscles can help to correct patella position and thus reduce pain and improve knee stability with a high riding patella - see knee strengthening exercises
• Patellar Taping: taping can also help to correct the position of the patella
• Ice Packs: regularly applying ice packs can help reduce pain and inflammation with symptomatic patella alta - see the ice wraps section
• Knee Brace: wearing a brace can help to reduce the symptoms of a high riding patella. Ideally, the brace should have a tubular section which sits above the kneecap to stop it riding up - see the knee brace section

Patella Baja / Infera

Patella Baja (sometimes called ‘Patella Infera’) is the opposite of patella alta. With patella baja the patella sits too low down (which is the same as the patellar tendon being too short). This leads to significantly increased patellofemoral contact pressures and very commonly leads to anterior knee pain, increased wear and tear to the articular cartilage, and eventually to articular cartilage damage and then patellofemoral arthritis.

Some people are simply born with patella Baja. Other potential causes include scarring and contraction of the patellar tendon after specific surgical procedures such as patellar tendon harvest for ACL reconstruction, or total knee replacement surgery.

Clinical presentation:

• Pain
• Decreased range of motion
• Swelling
• Extensor Log

Unfortunately, there are no effective surgical procedures available to treat/cure/reverse patella baja, and treatment effectively consists simply of activity modification (particularly avoiding squats, lunges, heavy weights and running/impact) and symptomatic relief (physiotherapy, anti-inflammatories etc).

Corrective measures

• Re-establishing the Joint line by use of distal Femoral augments
• Tibial tubercle Osteotomy with proximal displacement
• Lengthening of the Patellar tendon
• Shaving of the anterior portion of the Tibial polyethylene
• Placement of the Patellar implant in a cephalad position