Anterior knee pain is a common presenting symptom seen by physiotherapists, musculoskeletal doctors, and orthopaedic surgeons. There are a variety of causes, and in some cases, the exact cause may not be found.
Chondromalacia / Patellofemoral Pain Syndrome (PFPS)
Chondromalacia is the most common cause of chronic anterior knee pain. The condition represents a softening of the cartilage on the under surface of the patella (‘knee cap’). It is thought to occur due to abnormal compressive forces between the patella and the femur (‘Thigh bone’). While the exact mechanism is unclear, current thinking points towards a combination of factors that contribute. These include abnormal tracking of the patella, muscle imbalance around the knee, and over-use. While Chondromalacia typically affects adolescents / young adults, it can occur at any age. It is common for both knees to be affected.Patients will typically describe a vague discomfort/pain at the front of the knee, which is aggravated with exercise or prolonged sitting/squatting with the knees in a flexed position.The diagnosis is often made following a combination of a medical history, a thorough examination of the knee joint, and advanced imaging. An MRI scan is often performed to help exclude other pathology within the knee joint.
The goal of treatment is to restore the normal biomechanics of the patella gliding within the groove of the femur. The majority of the time, this can be managed with non-operative measures. These include an initial period of rest from exercises that aggravated the symptoms, a physiotherapy program designed at restoring the muscle imbalance, and weight loss if appropriate. The role of taping, or the use of knee braces, may provide benefit in some cases.
Do I need surgery?
While the majority of cases can be managed without surgery, sometimes chondromalacia is not cured by these conservative approaches. Surgical options include:
Through 2 small (5mm) incisions, an arthroscopy allows the surgeon to use a specialized camera to inspect the joint surfaces for signs of damage. When present, a ‘chondroplasty’ is performed via this ‘key hole’ technique, to re-contour the damaged cartilage surface.
In rare cases of combined chondromalacia and patella (‘knee cap’) malalignment, further surgical techniques may be required to improve the tracking of the knee cap and reduce the forces through this region.
Other causes of Anterior knee pain in adolescents
Osgood Schlatter disease (OSD) is common in active adolescents, and typically presents with gradual onset of pain below the knee, which is aggravated by running or jumping. OSD is also known as apophysitis of the tibial tubercle and represents inflammation of the patella tendon at its insertion into the tibia (shin bone). Treatment is generally conservative with a combination of rest, physiotherapy, and awaiting natural skeletal maturity with age. If symptoms persist into adulthood, surgical removal of these ossicles yields good results.
Bipartitie patella is a condition where the 2 separate growth centers for the knee cap fail to fuse together in early childhood. It is seen in 1-2% of the population and is usually an incidental finding, with only 2% of affected patients having symptoms.
Other causes of Anterior knee pain in adults
Arthritis affecting the undersurface of the knee cap (patella), or the groove that it sits in (‘trochlea’), is a common cause of anterior knee pain in middle and older age groups. Please refer to “Arthritis” for further information.
Patella Tendonitis is often referred to as ‘jumper’s knee’, and is seen in jumping athletes as an ‘over use’ injury. Patients present with pain just below the knee cap, that usually has gradual onset. Conservative management dominants the treatment, with a combination of rest, eccentric exercises, and a detailed physiotherapy program.
Bursitis represents inflammation of the normal bursae present around the knee joint. It can affect the bursae directly in front of the knee cap (‘Prepatellar bursitis’), below the knee cap (‘Infrapatellar bursitis’), or along the inside of the knee (‘Anserine bursitis’). The majority of cases respond to conservative management.