Kneecap (Patello Femoral) Problems
The patello femoral joint is the kneecap joint. It involves the kneecap running in a groove at the front of the thigh bone, rather like a rope travelling in a puley. Forces transmitted through this joint can be up to 5X body weight. The articular cartilage on the kneecap is very thick as a result.
Arthroscopy (Keyhole surgery) view of the kneecap joint (Kneecap on top, groove on bottom)
Adolescent anterior knee pain (chondromalacia patella) is a condition usually found in females in their late teens and early twenties. The underlying problem is not fully understood and may be multifactorial. The abnormality appears to be some softening of the cartilage under the kneecap, which is less tolerant of load and causes pain. There is usually no damage or major problem found within the knee and surgery is of no benefit except in diagnosing the condition. Treatment depends on modifying activities and avoiding excess loading of the kneecap combined with physiotherapy and most cases self resolve over a period of time with intermittent exacerbations and episodes along the way.
First time dislocation of an otherwise normal kneecap is a very painful event and occurs in sports or other situations when the knee is either twisted or a fall sustained with impact on the inner side of the knee driving the kneecap off to one side. After the kneecap is reduced which may involve sedation or light anaesthesia, the knee may be strapped up and kept in a splint for a period. Treatment also comprises the RICE regime of Rest, Ice, Compression, Elevation.
Recurrent dislocation of the kneecap can be a very complex problem in terms of cause and treatment. It requires a thorough understanding of the biomechanics and forces going across the knee and an assessment of any predisposing factors in the patient. Treatment is very variable from physiotherapy, bracing, or surgery and results are less predictable than in other areas of knee surgery.
Maltracking of the kneecap is usually a result of an imbalance between forces displacing the kneecap and muscle counteracting forces to stabilise it. Treatment usually is directed at correcting muscle strength in the appropriate muscles to reduce the imbalance.
Arthroscopic appearance of a Maltracking kneecap. Notice the knee cap sits completely off the groove as knee is bent from 0 degrees to 90 degrees.
X-ray of a maltracking kneecap before and after corrective surgery
Arthritis of the kneecap is an entity that can occur in conjunction with arthritis in the rest of the knee or in an isolated form in the kneecap. If it is advanced and part of general arthritis in the knee, then a knee replacement may be the definitive treatment if there are no other contraindications. If the arthritis is confined to the kneecap, a soft tissue release of tight structures if present may reduce symptoms and can be done through a keyhole procedure. For more advanced isolated arthritis of the kneecap, a partial knee replacement of just the kneecap joint may be feasible.