Softening of the Patellar Articular Cartilage
- Chondromalacia patellae literally means softening (Greek malakia) of the cartilage (chondros) of the patella - specifically the articular cartilage on the posterior surface of the patella - and it may progress through FIBRILLATION, FISSURING and EROSION; it is one of the most frequently encountered causes of knee pain in young people, classically young adults and often women.
- It is a DESCRIPTIVE term for a cartilage finding rather than a single pathophysiological diagnosis, and it overlaps with but is not synonymous with PATELLOFEMORAL PAIN syndrome - many patients with anterior knee pain have normal cartilage, and conversely chondromalacic change can be found without symptoms - so the diagnosis should not be assumed from pain alone, and 'idiopathic' chondromalacia is that arising without a clear anatomical cause.
- The ARTHROSCOPIC grading is the OUTERBRIDGE classification: grade I, softening and swelling of the cartilage; grade II, fragmentation and fissuring in an area of 1.5 cm or less; grade III, fragmentation and fissuring in an area larger than 1.5 cm; and grade IV, cartilage erosion down to exposed subchondral bone.
- CLINICALLY there is anterior or retropatellar knee pain that is typically worse with stair climbing/descending, squatting, kneeling and prolonged sitting (the 'theatre sign'), sometimes with crepitus; examination may show a positive CLARKE'S sign (pain on patellar compression during quadriceps contraction - the patellar grind test) and patellofemoral tenderness, and contributing factors such as maltracking should be sought.
- IMAGING is usually for exclusion and grading: radiographs (including a skyline/Merchant view) assess patellofemoral alignment and exclude other causes, while MRI can show cartilage signal change and grade the lesion; arthroscopy provides the definitive (Outerbridge) grading but is not required to make the clinical diagnosis.
- MANAGEMENT is predominantly CONSERVATIVE: activity modification, analgesia/NSAIDs, and a structured rehabilitation programme emphasising QUADRICEPS (especially VMO) and HIP/core strengthening, stretching and patellar taping/bracing; intra-articular options (e.g. hyaluronic acid, and platelet-rich plasma, which has shown benefit over physiotherapy alone in some studies, especially in younger patients) and arthroscopic chondroplasty or cartilage procedures are reserved for refractory cases.
- “Chondromalacia patellae = SOFTENING of patellar articular cartilage (-> fibrillation -> fissuring -> erosion); common anterior knee pain in young adults (often women).
- “DESCRIPTIVE term (a cartilage finding), overlaps with but is not the same as patellofemoral pain; graded arthroscopically by OUTERBRIDGE (I-IV; IV = exposed bone).
- “Anterior knee pain worse on stairs/squatting/prolonged sitting; positive Clarke's sign. Management CONSERVATIVE-first (VMO/hip rehab; injections/chondroplasty if refractory).
Softening of the patellar articular cartilage (progressing to fibrillation/fissuring/erosion); common anterior knee pain in young adults. Graded by Outerbridge (I-IV).
A descriptive term - overlaps with but is not the same as patellofemoral pain (which can occur with normal cartilage). Manage conservatively first.
Definition, Grading & Assessment
Chondromalacia patellae is softening of the articular cartilage on the posterior surface of the patella (Greek: chondros = cartilage, malakia = softening), which may progress to fibrillation, fissuring and erosion, and it is a common cause of anterior knee pain in young adults (often women). It is a descriptive cartilage finding rather than a single disease, overlapping with but not identical to patellofemoral pain (which can occur with normal cartilage). Cartilage change is graded arthroscopically by the Outerbridge classification (I softening/swelling; II fissuring in an area 1.5 cm or less; III fissuring in a larger area; IV exposed subchondral bone). Clinically there is anterior/retropatellar pain worse on stairs, squatting and prolonged sitting, with a positive Clarke's (patellar grind) sign; radiographs (with a skyline view) and MRI assess alignment and grade, but arthroscopy gives the definitive grading.
| Grade | Cartilage appearance |
|---|---|
| I | Softening and swelling of the cartilage |
| II | Fragmentation/fissuring in an area 1.5 cm or less |
| III | Fragmentation/fissuring in an area larger than 1.5 cm |
| IV | Erosion of cartilage down to exposed subchondral bone |
Management
- Conservative first: activity modification, analgesia/NSAIDs, and a structured rehabilitation programme emphasising quadriceps (VMO) and hip/core strengthening, stretching, and patellar taping/bracing.
- Address contributors: patellar maltracking, weak hip abductors/external rotators, tight lateral structures and biomechanical factors.
- Injections: intra-articular hyaluronic acid and platelet-rich plasma (which has shown benefit over physiotherapy alone in some studies, particularly in younger patients) for selected refractory cases.
- Surgery: arthroscopic chondroplasty/debridement or cartilage-restoration procedures are reserved for refractory, high-grade lesions, with realignment only for a demonstrated maltracking cause - because the pain often does not correlate well with the cartilage grade.
The key judgement in chondromalacia patellae is to remember that it is a descriptive cartilage finding, not a one-to-one explanation for a patient's pain: anterior knee pain frequently occurs with normal cartilage (patellofemoral pain), and chondromalacic change is sometimes found incidentally without symptoms, so the clinical picture and contributing biomechanical factors must be assessed rather than attributing all pain to the cartilage and rushing to surgery. Management is conservative first - quadriceps (VMO) and hip strengthening, activity modification and load management - with injections and arthroscopic chondroplasty or cartilage procedures reserved for genuinely refractory cases, and realignment surgery only for a demonstrated maltracking cause. Over-treating the radiological or arthroscopic grade rather than the patient is the pitfall to avoid.
Evidence & Key Studies
Chondromalacia patellae (definition and natural history)
- Chondromalacia patellae is softening of the articular cartilage on the posterior surface of the patella (chondros = cartilage, malakia = softening).
- It may eventually lead to fibrillation, fissuring and erosion of the cartilage.
- It is one of the most frequently encountered causes of knee pain in young people.
PRP and hyaluronic acid for anterior knee pain due to chondromalacia patellae
- Chondromalacia patellae describes softening of patellar articular cartilage and remains a general descriptive term not tied to a single pathophysiological mechanism; it commonly causes anterior knee pain in young adults (often women).
- In patients with anterior knee pain and a positive Clarke's sign without altered patellofemoral anatomy, platelet-rich plasma (with hyaluronic acid) improved VAS and Kujala scores significantly more than physiotherapy alone at 3 and 6 months.
- Younger patients benefited more from the injection treatment.
According to PubMed, the definition (softening of patellar articular cartilage progressing to fibrillation, fissuring and erosion) and its frequency as a cause of knee pain in young people come from the cited Gordon article; the characterisation of chondromalacia as a general descriptive term, the association with anterior knee pain and a positive Clarke's sign, and the benefit of PRP/hyaluronic acid over physiotherapy alone (particularly in younger patients) from the cited Ostojic study. The Outerbridge arthroscopic grading, the overlap with patellofemoral pain, and the conservative-first rehabilitation pathway are standard, well-established teaching. (See also our Patellofemoral Pain Syndrome and Patellar Instability topics.)
Clinical Decision Scenarios
Practise clinical reasoning and management decisions out loud
“What is chondromalacia patellae and how is it graded?”
“How would you manage a young adult with chondromalacia patellae?”
Mnemonics & Memory Aids
SOFTEN
Hook:SOFTEN: Softening, Outerbridge grades, Fibrillation/fissuring, Theatre-sign pain (Clarke's), Exercise rehab, Not equal to patellofemoral pain.
Definition
- Softening of the patellar articular cartilage (chondros + malakia)
- Progresses: softening -> fibrillation -> fissuring -> erosion
- Common anterior knee pain in young adults (often women); a descriptive term
Grading & assessment
- Outerbridge: I softening, II fissuring 1.5 cm or less, III fissuring over 1.5 cm, IV exposed bone
- Pain worse on stairs/squatting/prolonged sitting (theatre sign); positive Clarke's sign
- Radiographs (skyline view) + MRI for alignment/grade; arthroscopy = definitive grade
Key concept
- Overlaps with but is not the same as patellofemoral pain (can occur with normal cartilage)
- Pain does not correlate well with cartilage grade
- Can be an incidental finding
Management
- Conservative first: activity modification, analgesia, VMO/hip/core rehab, taping/bracing
- Injections (HA, PRP) for refractory cases
- Chondroplasty/cartilage procedures for refractory/high-grade; realignment only for maltracking