What is Trochlear Dysplasia?
Trochlear dysplasia is an abnormality in the shape of the vertical groove in the lower end of the femur or thigh bone which is known at the trochlear groove. It acts as a guide channel along which the kneecap or patella moves when the knee joint is flexed or extended. Trochlear dysplasia is a rather common abnormality of the knee that can cause severe symptoms and is often misdiagnosed.
Normal Anatomy of the Trochlear Groove
The patella is a sesamoid bone that is formed in the middle of the tendon that connects the femur and shin bone or tibia. The patella moves downward along the lower end of the femur when the knee is bent. The lower end of the femur has two rounded ends with the trochlear groove between them. The patella moves along this groove as the knee bends. The groove becomes flat at the top and is deeper lower down. This causes the patella to fit snugly within the trochlear groove when the knee is bent and less so when the knee is straightened. The lateral or outer wall of the groove is slightly higher than the inner or medial wall of the groove.
Causes of Trochlear Dysplasia
The anatomy of the trochlear groove may develop improperly and the groove may be very shallow or flat with the undersurface of the patellar mirroring this anatomy resulting in the patellar not fitting snugly within the trochlear groove. The groove may also be convex, forming a bump on the lateral wall and an under-formed medial side. In such instances, the patella becomes unstable when the knee is straightened.
Symptoms of Trochlear Dysplasia
Some of the signs and symptoms of trochlear dysplasia include:
- Knee aching and pain
- Feeling like the knee is about to give way
- Increased risk of patellar dislocation
Diagnosis of Trochlear Dysplasia
Trochlear Dysplasia may be diagnosed based on symptoms, physical examination of the knee and the following imaging studies:
- Lateral view X-ray which is taken from the side
- 45 degree patella sunrise X-ray, which is taken with the knee flexed and the X-ray beam parallel to the long axis of the tibia
- Ultrasound examination
- Magnetic resonance imaging
Treatment of Trochlear Dysplasia
Treatment for trochlear dysplasia will depend on the severity of the condition and the presence of other factors such as arthritis. The various options include:
Nonsurgical Treatment: This includes:
- Use of knee braces
- Physical therapy
Surgical Treatment: This can include:
- Trochleoplasty, which involves cutting and reshaping the bone to create a normal-shaped groove
- Medial patellofemoral ligament reconstruction
- Tibial tubercle osteotomy, which is the cutting and reshaping of a part of the tibia
- Distal femoral osteotomy, which is the cutting and reshaping of a part of the femur.