Chondromalacia patellae: kneecap pain, causes and treatment

The patella, or kneecap, sits in the tendon at the front of the knee and glides in a groove on the thigh bone as you bend and straighten the leg. The underside of the patella is covered in smooth cartilage. Chondromalacia patellae literally means softening of the kneecap cartilage, and Patient.info describes it as damaged cartilage behind the patella, like a softening or wear and tear.

Cambridge University Hospitals describes the overlapping term patello-femoral syndrome as an irritation of the kneecap and the underlying bone, caused by the patella not moving on the femur correctly when you bend and straighten your knee. If it is off-centre, it is pulled to one side in the groove and puts excessive stress on one part of the underside of the kneecap. The cartilage there may become inflamed, and you may hear or feel crunching sensations or pressure behind the kneecap.

In practice, the terms chondromalacia patellae, patellofemoral pain syndrome and anterior knee pain are often used for the same problem, because it is often not possible to prove that the cartilage is damaged and the management does not depend on the label.

Cambridge says you will probably experience pain with movements that involve bending the knee or with prolonged sitting. Patient.info says the pain is typically worse going up or down stairs, and may come with a grinding feeling or noise.

• A dull ache around or behind the kneecap.

• Pain going up or down stairs, squatting, kneeling or running downhill.

• Stiffness or pain after sitting with the knees bent, such as in a cinema or car.

• Crunching, grinding or clicking, usually painless.

• Sometimes a feeling that the knee is about to give way, though true locking or giving way suggests a different problem.

The reason cartilage damage occurs is not entirely clear, according to Patient.info. It is thought that the kneecap may rub against the lower part of the thigh bone instead of gliding smoothly. Some people have a slight alignment problem, which may be due to how the knee developed before birth or to an imbalance in the muscles around the knee, so that one side of the quadriceps pulls harder than the other. A combination of an alignment problem and overuse with sports is likely to be the most common reason.

Cambridge lists tight muscles or ligaments pulling the patella sideways, weak muscles not holding the patella in place, and biomechanics such as flat feet or overpronation, for which special insoles may be recommended. Patient.info adds that in older people it may develop as part of the ageing process, with wear and tear of cartilage in many joints.

Patient.info says a provisional diagnosis is usually made from the symptoms plus an examination of the knee, and that no tests are usually needed because treatment can be started on the basis of a working diagnosis. A GP or physiotherapist will usually check how the kneecap moves, the strength and flexibility of the thigh and hip muscles and how you squat or step.

If the diagnosis is not clear or symptoms do not improve after treatment, tests may be requested. Patient.info lists blood tests and a standard knee X-ray to help rule out some types of arthritis or inflammation, an MRI scan, which shows details of the knee joint and can show up some cases of chondromalacia, and arthroscopy, in which a tiny camera is inserted into the knee.

Patient.info says evidence shows that conservative measures work better than surgical options, that exercises have been shown to be most effective, and that painkillers and taping have not been shown in studies to have long-term benefits. The usual treatment advised is to avoid overuse of the knee and to have physiotherapy, which is effective in most cases.

Cambridge's physiotherapy leaflet describes exercises designed to address tight muscles, weak muscles and alignment: step-ups, single leg dips, lunges, patellar mobilisations, iliotibial band and quadriceps stretches, a wall-slide tracking exercise, an inner-thigh muscle (vastus medialis oblique) activation exercise and a hip flexor stretch. Your physiotherapist will advise which are suitable for you and how many repetitions to do.

The NHS knee pain advice suggests, at first, putting as little weight as possible on the knee, using an ice pack or frozen peas wrapped in a tea towel for up to 20 minutes every 2 to 3 hours, and painkillers such as paracetamol or ibuprofen gel or tablets, and seeing a GP if the pain does not improve within a few days.

Return to sport gradually. Cut back on activities that provoke pain, such as deep squatting, running downhill and lots of stairs, and build up again as strength improves. Footwear, running technique and training load can all be reviewed by a physiotherapist.

The NHS advises getting advice from 111 now if your knee is very painful, you cannot move it or put any weight on it, it is badly swollen or has changed shape, it locks, gives way or painfully clicks (painless clicking is normal), or you have a very high temperature or feel hot, cold or shivery with redness or heat around the knee, which can be a sign of infection.

A hot, red, swollen knee with fever needs same-day assessment. Chondromalacia patellae on its own does not cause these signs.

Patient.info says the outlook is good and most people get better with simple treatments such as physiotherapy. Improvement is usually gradual over weeks to months, and consistency with exercises matters more than intensity. Some people continue to have flares with heavy training and need to keep a maintenance programme going.

If symptoms persist despite a proper trial of physiotherapy, a review by a sports medicine or orthopaedic specialist can look for other causes, such as kneecap instability, tendon problems or early arthritis.

On the NHS the route is the GP or a self-referral physiotherapy service, where available, with orthopaedic or sports medicine referral if there is no improvement. Imaging is not routine for typical kneecap pain.

Private physiotherapists and sports medicine clinics can offer quicker access. Since exercise therapy is the key treatment, the main thing is a structured, progressive plan with review rather than passive treatments alone.