Anterior knee pain simply describes the symptoms of pain at the front of the knee no matter what the cause. It is a very common condition
The symptoms are of pain at the front of the knee or behind the kneecap, though on occasion referred pain is also felt deep behind the knee. The pain is made worse by going up and especially down stairs or slopes, prolonged sitting, kneeling or squatting, and lifting heavy items. The knee can also feel as though it has become stuck or give way. The can seem "puffy", but significant swelling is unusual. You may be aware of a crunching sensation in the knee which can even be heard by others.
The pain arises in the joint between the kneecap and thighbone (patello-femoral joint). The kneecap acts like a pulley, allowing the thigh muscles (quadriceps) to pull the knee straight. To function well, the kneecap has to sit and move centrally as it tracks in a groove on the front of the thighbone (trochlea).
Muscle imbalance: The control, strength and balance of the muscles around the kneecap will influence tracking.
Mal-alignment: Some people have abnormal anatomy around the knee that leads to mal-tracking.
Trauma: Some people develop anterior knee pain after a hard blow to the front of the knee such as a heavy fall or if the knee is driven into the dashboard in a car accident. Occasionally damage to the joint results from the injury, but many times the pain is actually difficult to explain.
Chondromalacia patellae: This term describes changes of softening or blistering of the joint surface (articular cartilage) behind the kneecap. For most people the cause is unknown and it can develop even in teenagers. It seems to be a self limiting problem that resolves with full skeletal maturity in the majority of these cases.
Osteoarthritis: This is a degenerative failure of the joint surface of the knee and it can be isolated to the patella-femoral joint.
Bi-partite patella: A congenital abnormality of the kneecap where it develops with a separate segment usually to the upper and outer side of the main kneecap.
Patellar tendonitis: A painful chronic inflammatory change in the tendon just below the kneecap usually due to overuse.
Despite the list of related and causative conditions, many cases of anterior knee pain remain difficult to explain.
Most patients only need assessment by taking a good history and examining the knee and limb. Occasionally an X-ray may be needed and even more rarely, a MRI scan, Ultra-sound scan, CT scan or even an isotope bone scan may be needed. Your surgeon will explain why they are being done.
Most patients will be managed by advising maintenance of ideal body weight and physiotherapy. The emphasis is on this being a condition that the patient should manage rather than receiving extensive treatment.
Specific exercises will be taught that help to control the kneecap as well as addressing areas such as overall posture and core stability. Taping, stretching and electrical stimulation of the muscles may also be used.
By the mechanics of the way the kneecap works, a loss of 2 stones weight translates into a reduction of 14 stones across the painful joint. The effect of weight can be demonstrated by climbing stairs whilst carrying heavy shopping.
A podiatrist will assess the effect of your foot alignment on how the kneecap functions. By putting a small insert into your shoe (an orthotic), the tracking of the kneecap can be improved and symptoms alleviated.
The vast majority of patients with anterior knee pain do not need to see a surgeon or consider an operation. In certain circumstances though, surgery is indicated. Operations for anterior knee pain are not uniformly successful and require prolonged rehabilitation.
Injections: Various injection treatments can be used including injecting steroids or hyaluronic acid into the knee joint, or local injections into the area around the patellar tendon or fat pad - usually perfumed under ultra-sound control.
Arthroscopy: Simply looking in the knee to see if there is a correctable cause is best avoided. The discomfort of the procedure can set back the progress physiotherapy can achieve and can make the symptoms worse.
Lateral release: This was a popular operation to re-align the kneecap. It may help in a very small number of cases where excessive tension in the soft tissues to the outer side of the patella can be proven but the results are unpredictable and recovery frustratingly slow.
Patellar realignment: This is a more extensive operation to correct significant anatomical abnormalities that have led to painful mal-tracking and physiotherapy has failed to help. Various operations may be used depending on the underlying problem. Careful analysis of the situation is vital to ensure the correct operation is used.
Replacement: In severe isolated osteoarthritis of the kneecap (patella-femoral joint) then it can be resurfaced with a plastic dome and a metal liner inserted into the worn groove on the thighbone. This is a much lesser operation than total knee replacement and is described in its own section. It is appropriate for only a small number of patients.
Most patients respond well to weight loss and physiotherapy. Adolescents with anterior knee pain also usually settle as they get older. For those requiring surgery, the results are usually good providing the right operation is chosen for the right reasons.