M22.4: Chondromalacia patellae

The cartilage on your kneecap is damaged.

The knee joint connects the thigh to the lower leg. The knee joint is made up of 3 bones. These bones are the thighbone (femur), the shinbone (tibia) and the kneecap. The kneecap usually sits in a groove in the thighbone. The bones in the knee joint are lined with a layer of cartilage. The knee joint is encircled by a capsule of connective tissue.

The kneecap is embedded in a tendon of a muscle. This muscle pulls from the thighbone and from the hip to the shinbone and extends the knee. The kneecap helps this muscle to transfer force more effectively. The kneecap also reduces the friction between the tendon and the thighbone.

The cartilage on the kneecap can be damaged if the kneecap comes under too much strain. The cartilage may also get damaged if the position of the kneecap in the groove of the bone changes.

The cartilage damage can cause pain in the knee, for example when you straighten up from squatting. The knee may also be swollen.

Additional indicator

On medical documents, the ICD code is often appended by letters that indicate the diagnostic certainty or the affected side of the body.

  • G: Confirmed diagnosis
  • V: Tentative diagnosis
  • Z: Condition after
  • A: Excluded diagnosis
  • L: Left
  • R: Right
  • B: Both sides

Further information


This information is not intended for self-diagnosis and does not replace professional medical advice from a doctor. If you find an ICD code on a personal medical document, please also note the additional indicator used for diagnostic confidence.
Your doctor will assist you with any health-related questions and explain the ICD diagnosis code to you in a direct consultation if necessary.


Provided by the non-profit organization “Was hab’ ich?” gemeinnützige GmbH on behalf of the Federal Ministry of Health (BMG).