Chondromalacia Patellae

Chondromalacia patella is softening and wear of the cartilage on the underside of your kneecap. This page explains what causes it, the symptoms, how it is diagnosed and treated, and when surgery is considered.

What is chondromalacia patella?

Your kneecap (patella) glides up and down a groove at the end of your thigh bone (femur) as you bend and straighten your knee. This groove is called the trochlea. The underside of the kneecap is covered with smooth cartilage, which lets it slide with little friction. In chondromalacia patella, this cartilage softens, frays or wears thin.

You may also see it written as chondromalacia patellae, which is the Latin form. It overlaps with patellofemoral pain syndrome, a term for pain around the kneecap whether or not the cartilage is damaged.

How is the damage graded?

Doctors grade the damage from 1 to 4, based on what they see on an MRI scan or during keyhole surgery:

• Grade 1: the cartilage is soft or swollen.
• Grade 2: there are shallow cracks in the surface.
• Grade 3: deeper cracks reach down towards the bone.
• Grade 4: the cartilage has worn through and the bone underneath is exposed.

What causes chondromalacia patella?

It often happens when the kneecap does not run centrally in its groove. This overloads part of the cartilage. Things that can affect how the kneecap tracks include:

• Weak hip and thigh muscles, especially the inner part of the quadriceps (the vastus medialis obliquus)
• The way your thigh and shin bones are aligned or rotated
• Flat feet that roll inwards (pronated feet)
• A tight iliotibial band, the strip of tough tissue down the outside of your thigh.

Repeated loading from running, jumping or squatting, a direct blow to the front of the knee and a previous kneecap dislocation can also damage the cartilage. In older people, it can be an early stage of arthritis behind the kneecap.

What are the symptoms of chondromalacia patella?

The main symptom is pain at the front of the knee, around or behind the kneecap. It is usually worse with activities that load the kneecap, such as walking up or down stairs, running, lunging, squatting or kneeling. Sitting for a long time with your knees bent can also bring it on. You may feel or hear grinding under the kneecap, and the knee can swell a little after activity. Both knees can be affected.

When should you see a doctor?

See your GP or physiotherapist if knee pain has not settled after a few weeks of rest and simple exercises. Seek medical advice sooner if:

• Your knee swells quickly, locks or gives way
• Your kneecap slips out of place (see patellofemoral instability)
• The pain wakes you at night
• Your knee is hot, red and swollen, or you have a fever. Seek urgent care.

How is chondromalacia patella diagnosed?

The diagnosis is mostly made from your symptoms and an examination of how your kneecap moves and how strong your hip and thigh muscles are. X-rays, including a view looking down on the kneecap, show its position and any arthritis. An MRI scan shows the cartilage in more detail.

Cartilage changes are common on MRI scans, even in people with no knee pain, and they become more common with age.^[4] So a scan is read together with your symptoms and examination, not on its own.

How is chondromalacia patella treated without surgery?

Most people are treated without surgery. Treatment aims to reduce the load on the kneecap and help it run centrally in its groove. International expert guidance recommends exercise therapy as the main treatment, often combined with other measures.^[1][2]

Exercise and physiotherapy

A physiotherapist can guide a program to strengthen your hip muscles and quadriceps and to stretch a tight iliotibial band. Strengthening the hip and knee muscles together reduces pain and improves function more than knee exercises alone.^[3] Improvement usually takes several weeks to months of regular exercise.

Changing your activities

For a while, cut back on activities that load the kneecap heavily, such as deep squats, lunges and running downhill. The aim is to reduce your pain, not to stop exercising altogether.

Foot orthotics

Shoe inserts (orthotics) can ease pain in the short term for some people, especially if your feet roll inwards.^[1]

Taping and braces

Taping the kneecap with the McConnell technique, or wearing a brace that supports the kneecap, aims to hold it in a more central position. The evidence for these is mixed. Some people find they ease pain enough to make exercise more comfortable.^[1][2]

When is surgery considered?

Surgery is not a treatment for chondromalacia patella, even when the pain has lasted a long time. In a randomised trial of people with long-standing kneecap pain, adding keyhole surgery (arthroscopy) to a home exercise program gave no better results than the exercise program alone, at 9 months and again at 5 years.^[5][6] Exercise remains the treatment. If your pain has not settled after a thorough program, your GP or physiotherapist can look again at the diagnosis and adjust your exercises.

What is the outlook for chondromalacia patella?

Damaged cartilage does not grow back, but the pain often improves with the right exercise program. Recovery can be slow. In one study, about 4 in 10 people had not recovered well 12 months after starting treatment,^[7] and in a smaller follow-up, more than half still had symptoms 5 to 8 years later.^[8] People whose pain had lasted longer before treatment tended to recover more slowly,^[7][8] so it is worth starting treatment early.

In the same long-term study, 48 of 50 people had no signs of arthritis on X-ray 5 to 8 years later.^[8]

References