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Chondromalacia Patella N011

Document
Last amended 
26 October 2015

Current RMA Instruments:

Reasonable Hypothesis SOP
79 of 2010
Balance of Probabilities SOP
80 of 2010
Changes from Previous Instruments:

SOP Bulletin 146

ICD Coding:
  • ICD-9-CM Codes: 717.7
  • ICD-10-AM code M22.4
Brief description

Chondromalacia patella is inflammation of the underside of the patella (knee cap) and softening of the cartilage.  It is one of a number of causes of anterior knee pain and is a common condition in young adults.  The SOP covers chronic pathology of the patella cartilage only.  The condition needs to be distinguished from other forms of patello-femoral pain syndrome and also osteoarthritis and acute cartilage tear involving the patella.  See further comments below.

Confirming the diagnosis:

To confirm the diagnosis there needs to be recurrent or chronic patellofemoral pain and evidence of softening, fibrillation, or loss of patella cartilage consistent with chondromalacia, seen on arthroscopy or imaging (CT scan or MRI scan).

The relevant medical specialist is an orthopaedic surgeon.

Additional diagnoses which may be covered by this SOP (further information required)
  • Patello-femoral pain syndrome – only where there are definite patella changes seen on MRI scan or arthroscopy.

  • Patello-femoral syndrome – as above

  • Runner's knee

Conditions that are excluded from this SOP
  • Acute articular cartilage tear* of the knee

  • Bipartite patella#

  • Chondromalacia of femoral condyle / trochlear grove#

  • Dislocation* of patella

  • Fracture* of the patella

  • Internal derangement of the knee*

  • Knee pain of unexplained origin#

  • Osteoarthritis* of the knee

  • Osteoarthritis* of the patello-femoral joint

  • Osteochondritis dissecans#

  • Patella maltracking#

* another SOP applies  - the SOP has the same name unless otherwise specified

# non-SOP condition

Clinical onset

Once the diagnosis has been confirmed, the clinical onset can be backdated to the onset of relevant recurrent or chronic symptoms.  If there was an initiating acute trauma the onset will not be at the time of that trauma, it will be some time (generally weeks to months) after that event when acute symptoms have resolved and the chondromalacia and its associated symptoms have had time to develop.

Clinical worsening

Treatment of chondromalacia patella generally involves reducing the volume of activities (e.g. running) that lead to pain, together with an exercise program to improve leg and core strength and stability.  Medication is generally not indicated other than for short term pain releif.  Surgery has not been shown to be effective.  Worsening can occur, particularly if activities that cause symptoms are continued or resumed at previous levels, or if a new acute injury to the knee is sustained.  The natural course varies.  The condition may resolve in some people but progress in others.

Further comments on diagnosis

Patello-femoral pain syndrome (PFPS) is a loose diagnostic label that covers various forms of anterior knee pain.  Cases with confirmed patella cartilage pathology consistent with the chondromalacia patella (CMP) SOP definition come under the CMP SOP.  Other cases will be non-SOP or covered by another SOP.  A more precise diagnosis than PFPS should be obtained where possible.

CMP involves the knee patella articular cartilage but not the rest of patellofemoral joint (femoral condyles or trochlea groove). Articular cartilage pathology at these sites would be covered by either the acute articular cartilage tear or osteoarthritis SOPs.

The CMP SOP covers chronic pathology of the patella cartilage.  The SOP for acute articular cartilage tear covers acute chondral tears of the patella.

There is a recognised diagnostic overlap between CMP and osteoarthritis of the patellofemoral joint and CMP can naturally progress to osteoarthritis.  CMP is the appropriate diagnosis when there is little other evidence of pathology apart from chondral lesions on the patella.  More extensive pathology with bony changes including subchondral sclerosis and osteophytes; and with more regions of the knee affected would warrant a diagnosis of osteoarthritis.  Generally, chondromalacia patella would not be a diagnosis provided in addition to osteoarthritis of the knee but may have been a past diagnosis.

In arthroscopy reports the term osteoarthritis may be used interchangeably to mean acute chondral defects or chondromalacia.   An examination of all data on file including the operation report and knee imaging would be required to formulate the correct diagnostic label.