KneeCap Maltracking and Management
If the knee cap (patella) is shifting out of place on bending or straightening it, the person may be dealing with patellofemoral maltracking (PFM).
The knee is the largest joint in your body which is formed of the tibio-femoral and patellofemoral joint. The Patellofemoral joint is formed by the kneecap or Patella sitting over a groove (trochlea) on the lower end of the thigh bone or femur.
It helps in an effective transmission of the forces of the knee movements across the joint. Patellar Maltracking occurs due to an imbalance between the dynamic relationship of the patella and trochlea during the normal range of motion of the knee.
To understand patellar maltracking first we will have to take a look into understanding how patella helps our leg to bend (flex) and straighten (extend) smoothly. The patellofemoral joint functions as a pulley for the quadriceps muscle to facilitate knee extension and reduce friction.
It is subjected to large amounts of load acting as a pulley. To provide better flexibility and maintain its functions both the bones have ligaments and cartilage to provide support and protection against instability. A small amount of side to side excursion is normally present. Tight tissues(ligaments and tendons) on the inner and outer side of the knee provide stability to the knee cap.
Undue stress on the patellofemoral joint from maltracking will lead to loss and attrition in the articular cartilage of the patellofemoral joint leading to early osteoarthritis with severe limitations of day to day life.
- Anterior Knee Pain: A chronic pain usually in front of the knee.
- Knee Giving Away: Symptoms of knee giving away may be present especially while walking or running. This may be associated with a sensation of grinding or popping every time the knee is moved. When they try to extend their knee it may feel like getting caught or the feeling that the knee won’t support them on standing.
- Episodes of dislocation: At times the patella might dislocate with excruciating pain and swelling. They may be able to relocate the patella by themselves but the episodes become frequent damaging the cartilage.
Causes & Predisposing Factors
Traumatic Injuries : Athletes and people who are physically active may suffer from injuries surrounding the knee cap which is why patellar maltracking disorder often affects young active adults. Often chronic overuse with underlying loss of structural support will lead to patellofemoral maltracking.
- Hereditary dysplastic knee cap : People may have a inherited malformed/dysplastic knee cap or the Trochlea. The dysplastic bone does not move into the set tract leading to instability
- Patella Alta : A high riding patella (Patella Alta) often leads to instability and maltracking. These patients often have a generalised inherited joint laxity.
- Others : bow legs (genu valgum), congenital intoeing (increased femoral anteversion, tibial torsion), tight or lax stabilizing structures on either side of the patella cause patellofemoral maltracking.
Early diagnosis is essential to prevent or stop the progression of cartilage loss and osteoarthritis.
- History : A detailed history about the clinical symptoms and restrictions of activity is taken.
- Physical Examination : For the physician to understand the dynamic movement of the patella commonly referred to as Patellar Tracking a thorough physical examination of the knee becomes necessary. The physician will conduct some clinical tests and take measurements.
- Q Angle : Q angle is an imaginary angle between the thigh and the patella which is used to measure the degree of patellar engagement in the trochlea. Increased Q angle is usually associated with PFM.
- Imaging : Assessment includes radiograph (x-ray) which is helpful in acute presentation. MRI and CT imaging may be needed and are superior modalities in looking for predisposing factors. MRI allows detailed evaluation of the morphology and structure of the joint especially helpful in guiding operative management.
The goal is to recreate the stable dynamic relationship between the patella and the trochlea with a knee which is pain free. Many different approaches have been advocated for treatment. Management can be nonoperative or operative which depends on the severity of the disease.
Nonoperative treatment generally consists of the use of anti-inflammatory medications, a short period of immobilization, followed by a focused physiotherapy regime with emphasis on range of motion, closed chain exercises, and vastus medialis obliquus (VMO) strengthening.
Recurrent patellar instability still occurs in between 15 and 45% of patients treated nonoperatively. Also the patients return to active sports can be as low, leaving many patients searching for further management options.
Operative management can be categorized as soft tissue procedures i.e not involving the bony structures and bony procedures.
Soft tissue Surgeries
Soft tissue procedures are used to repair or tighten loose and stretched soft tissues or release of the tight ligaments that contribute to patellar instability. They are best indicated in isolation in the setting of recurrent instability with minimal underlying bony malalignment.
Lateral Release :
A commonly used procedure is lateral release which is a knee arthroscopic surgery. Surgery is performed through small incisions and the tight ligament on the outer knee cap is released so as to allow the knee cap to settle towards the inside of the trochlea.
Medial PatelloFemoral Ligament (MPFL) Repair
Reconstruction of the Medial Patellofemoral Ligament (a ligament stabilising the inner side of patella preventing outward dislocation) is a procedure usually done for recurrent lateral patellar instability. The ligament provides vital inner side support to the patella. The ligament is tightened to provide stability to the knee cap.
When the underlying cause is bony malalignment, procedures such as:
- Osteotomy : Tibial tubercle (part of tibia providing attachment to patellar tendon) transfer osteotomy can be performed. It involves cutting of the bone and changing the insertion of the patellar tendon, the procedure ultimately affect the position of patella engaging in the trochlea during range of motion. It also prevents the damaged articular cartilage from coming in contact therefore reducing pain and increasing stability.
- Trochleoplasty : Lastly a procedure known as trochleoplasty may be indicated in the patient with significant trochlear dysplasia/malformation causing PFM. This procedure involves altering the shape of the trochlea so that the patella engages in the trochlea effectively during the range of motion.
If you have any above said symptoms or may think you’re suffering from patellar maltracking disorder, consider visiting an orthopaedic surgeon with expertise in knee arthroscopy.