Patellar maltracking is said to occur when the patella does not move within the patellar groove of the lower femur. The patella is a sesamoid bone contained within the quadriceps tendon [the portion between the patella and tibial tuberosity is called patellar tendon]. The movement of the patella and its tendon is greatly influenced by forces around it.
Patellar maltracking is one of the important causes of knee problems. Patella or kneecap bone is moved by actions of quadriceps femoris which is composed of four different parts. Two of these parts are named as vastus lateralis and vastus medialis, and pull the patella during the knee movement to lateral and medial side respectively.
An imbalance of these forces is a very common cause of patellar maltracking.
Mostly, it is the vastus lateralis [lateral or outer pull] which is overactive and stronger than the vastus medialis [medial or inner pull]. Due to this imbalance, the patella gets pulled out of the groove resulting in increased friction with the femur and eventually pain.
When the forces are too unmatched, even patellar dislocation could result.
Causes of Patellar Maltracking
Maltracking of the patella may be caused by various factors –
- Muscular imbalance
- Joint surface malalignment
- Excessive knee valgus [increases lateral forces]
- Quadriceps contractures
- Joint overuse
- Excessive loading of joint
- Relatively flat patella
- Patella alta (high-riding patella),
- Shallow femoral trochlea
- Femoral torsion
- Loose medial structures
- General joint laxity
The most common form of malalignment is rotational malalignment, whereby the patella is tilted.
Assessment of Maltracking
Patellar maltracking or malalignment is assessed by measurements on radiographs and CT.
Q angle is the angle between a line joining the anterior superior iliac spine and the center of the patella, and a line joining the center of the patella and the tibial tuberosity. This reflects the degree of valgus force upon the patella. The normal value is about 15 degrees. A large Q angle is a predisposing factor.
Tibial Tubercle – Trochlea Groove Distance
The trochlear groove is the concave surface where the patella makes contact with the femur. Tibial tubercle – trochlea groove distance compares the position of the trochlea groove with the tibial tubercle. Two axial CT slices are superimposed, one at the level of the trochlear groove and the other at patellar tendon tibial attachment distance greater than 1.8-2 cm has high specificity for maltracking.
Patellar Maltracking Treatment
Most of the cases of patellar maltracking are managed by nonoperative treatment. The strategies and options include
- Relative rest – curtailing and modification of activity
- Quadriceps strengthening
- Icing of the knee after the activity
- Footwear modification
- Drugs for pain like NSAIDs
- Hip, hamstrings, iliotibial band and claves stretching
- Taping of knee
Treatment needs to be individualized.
Surgery may be considered when the patient does not improve on nonoperative treatment and consist of procedure that addresses the cause. For example, the lateral release is done for muscle imbalance. Arthroscopic procedures may be done for joint pathologies.