Chondromalacia Patellae: A Complete Review for Patients and Clinicians
Chondromalacia patellae, often referred to as “runner’s knee,” describes the softening, fissuring, and eventual degeneration of the articular cartilage on the undersurface of the patella. It is one of the most common causes of anterior knee pain, particularly among adolescents, young adults, and athletes. While often self-limiting with proper management, untreated or mismanaged cases can progress to patellofemoral osteoarthritis. This comprehensive review synthesizes current evidence on pathophysiology, clinical evaluation, advanced imaging—including MRI interpretation—and both nonoperative and operative treatment strategies, with practical guidance for patients and clinicians alike.
Anatomy and Pathophysiology
The patellofemoral joint is a critical biomechanical structure formed by the articulation between the posterior facet of the patella and the femoral trochlear groove. The patella functions as a sesamoid bone embedded within the quadriceps tendon, enhancing the lever arm and force transmission of the extensor mechanism. Its articular surface is covered by 3–5 mm of hyaline cartilage—the thickest in the human body—designed to distribute compressive loads that can exceed 7 times body weight during deep knee flexion.
In chondromalacia, abnormal mechanical stress disrupts cartilage homeostasis. Contributing factors include:
- Patellar maltracking: Due to muscle imbalances (weak VMO, tight lateral retinaculum)
- Limb malalignment: Genu valgum, femoral anteversion, external tibial torsion (“miserable malalignment syndrome”)
- Patella alta: High-riding patella delays engagement with the trochlear groove
- Overuse: Repetitive impact in running, jumping, or squatting sports
- Rapid growth: Common in adolescents during growth spurts
Cartilage breakdown itself is painless, but secondary inflammation of the synovium, subchondral bone, and infrapatellar fat pad generates the characteristic anterior knee pain.
Epidemiology
Chondromalacia patellae disproportionately affects young, active individuals:
| Factor | Details |
|---|---|
| Age | 12–25 years (peak during adolescence) |
| Gender | Women > Men (2:1 to 3:1 ratio due to wider pelvis and increased Q-angle) |
| At-Risk Populations | Runners, cyclists, basketball/volleyball players, dancers, military recruits |
| Key Risk Factors | Flat feet, knock-knees (genu valgum), quadriceps weakness, obesity, sudden increase in activity load |
Clinical Presentation
Patients typically describe a gradual onset of dull, aching pain in the front of the knee, often poorly localized. Pain is aggravated by activities that increase patellofemoral joint reaction forces:
- Prolonged sitting with knees bent (“theater sign”)
- Walking downstairs or downhill
- Squatting, kneeling, or lunging
- Standing up from a seated position
Physical examination may reveal:
- Quadriceps atrophy (especially vastus medialis obliquus)
- Positive patellar grind test (pain during compression + active knee extension)
- Palpable or audible crepitus during knee flexion
- Reduced medial patellar glide
- Lateral patellar tilt on skyline view
Imaging and MRI Diagnosis
While diagnosis is primarily clinical, MRI is the gold standard for confirming cartilage pathology and grading severity using the Outerbridge classification.
MRI sequences such as T2-weighted fat-saturated or proton density are optimal for visualizing cartilage integrity. Abnormal cartilage appears as high signal intensity, surface irregularity, or focal defects.
| Outerbridge Grade | MRI Findings | Clinical Relevance |
|---|---|---|
| I | Softening, swelling, increased T2 signal | Reversible with conservative care |
| II | Surface fissures or blistering | Responds well to physical therapy |
| III | Partial-thickness cartilage loss | May require extended rehab; consider biomechanical correction |
| IV | Full-thickness defect with exposed subchondral bone | Risk for osteoarthritis; surgical options may be considered |
Nonoperative Management (First-Line Therapy)
Conservative treatment is successful in over 90% of cases when implemented correctly and consistently.
1. Activity Modification
- Avoid aggravating activities (deep squats, lunges, hill running) during acute phase
- Replace high-impact exercise with swimming, cycling (low resistance), or elliptical training
2. Targeted Physical Therapy
A comprehensive program should include:
- VMO activation: Short-arc quads (0°–30°), straight leg raises with medial rotation
- Hip strengthening: Clamshells, side planks, hip abduction
- Hamstring and IT band flexibility: Foam rolling, static stretching
- Neuromuscular control: Single-leg balance, step-down drills
3. Adjunctive Interventions
- Patellar taping or bracing: McConnell taping or off-the-shelf patellar stabilizers improve alignment and reduce pain during activity
- Foot orthotics: Custom or prefabricated insoles for patients with pes planus or excessive foot pronation
- NSAIDs: Short-term use for pain and inflammation (e.g., ibuprofen 400 mg TID for 5–7 days)
- Icing: 15–20 minutes after activity to control inflammation
Operative Treatment (Refractory Cases)
Surgery is reserved for patients with persistent, disabling symptoms after 6–12 months of dedicated conservative therapy and documented structural pathology on imaging.
| Procedure | Indications | Key Considerations |
|---|---|---|
| Arthroscopic debridement | Mechanical symptoms (catching, grinding) with Outerbridge Grade II–III lesions | Palliative only; does not alter disease progression |
| Lateral retinacular release | Confirmed lateral tightness + fixed lateral patellar tilt on MRI/skyline X-ray | Avoid isolated release; best combined with medial reefing or realignment |
| Tibial tubercle osteotomy (e.g., Fulkerson) | Patella alta, elevated TT-TG distance (>20 mm), recurrent instability | Anteromedialization reduces patellofemoral pressure; requires 6+ months rehab |
| MPFL reconstruction | History of dislocation or subluxation with ligamentous insufficiency | Often combined with osteotomy in complex cases |
Note: Intra-articular injections (corticosteroids, hyaluronic acid, PRP) have limited evidence in chondromalacia and are not routinely recommended.
Prognosis and Prevention
With consistent adherence to physical therapy and activity modification, most patients experience significant symptom improvement within 3–6 months. Full cartilage regeneration is unlikely, but functional recovery is excellent.
Preventive strategies include:
- Pre-participation screening for biomechanical risk factors
- Strength and flexibility programs focused on hips and quadriceps
- Gradual progression in training intensity (avoid “too much, too soon”)
- Proper footwear with arch support for flat-footed individuals
- Maintenance of healthy body weight to reduce joint loads
Frequently Asked Questions (FAQs)
For Patients
Q: Will my cartilage grow back?
A: Mature articular cartilage has limited regenerative capacity. However, symptoms often resolve even without structural healing through improved biomechanics and muscle support.
Q: Can I return to sports?
A: Yes—once pain-free during daily activities and with adequate strength/flexibility. A gradual return-to-sport protocol under therapist guidance is essential.
Q: Do I need surgery?
A: Rarely. Over 90% of cases improve with physical therapy, bracing, and activity modification.
Q: Is chondromalacia the same as arthritis?
A: It’s an early form of cartilage damage. If managed properly, it does not necessarily progress to osteoarthritis.
For Clinicians
Q: When should I order an MRI?
A> Reserve MRI for patients with persistent pain beyond 3 months of PT, mechanical symptoms, or atypical presentation. It’s not needed for initial diagnosis.
Q: How do I differentiate chondromalacia from PFPS?
A> Patellofemoral pain syndrome (PFPS) is a clinical diagnosis without confirmed cartilage damage. Chondromalacia implies structural degeneration (MRI-confirmed). In practice, “PFPS” is preferred early; “chondromalacia” when imaging confirms pathology.
Q: What’s the most effective physical therapy protocol?
A> Programs combining hip and quadriceps strengthening, neuromuscular control, and movement retraining show the best outcomes (Collins et al., Br J Sports Med 2018).
Q: Are injections useful?
A> Corticosteroids offer short-term relief but no long-term benefit. PRP and viscosupplementation lack high-quality evidence in diffuse chondromalacia.
Conclusion
Chondromalacia patellae is a prevalent yet manageable condition rooted in biomechanical dysfunction rather than irreversible joint damage. Early recognition, patient education, and a structured, individualized rehabilitation program form the cornerstone of successful management. The inclusion of MRI, as demonstrated in the images above, allows for precise grading and tailored intervention. With proper care, most patients return to full activity without long-term sequelae—highlighting the critical role of conservative therapy in preserving joint health and function.
References
- Fulkerson JP. Anterior knee pain and patellofemoral malalignment. J Bone Joint Surg Am. 2008;90(12):2738–2748.
- Outerbridge RE. The etiology of chondromalacia patellae. J Bone Joint Surg Br. 1961;43-B:752–757.
- Collins NJ, et al. Consensus statement on exercise therapy and physical interventions for patellofemoral pain. Br J Sports Med. 2018;52(18):1170–1178.
- OrthoBullets. Idiopathic Chondromalacia Patellae. https://www.orthobullets.com/knee/4055/idiopathic-chondromalacia-patellae. Updated May 2021.
- Arthritis Foundation. Chondromalacia Patella (Runner’s Knee). https://www.arthritis.org/diseases/chondromalacia-patella
- KidsHealth New Zealand. Chondromalacia Patella (Runner’s Knee). https://www.kidshealth.org.nz/chondromalacia-patella
- Witvrouw E, et al. Stretching and strengthening exercises in patellofemoral pain syndrome: a randomized controlled trial. Br J Sports Med. 2009;43(4):277–282.
- Smith TO, et al. Operative versus non-operative management for patellofemoral pain: a systematic review. Knee. 2020;27(1):1–10.