Knee Cartilage Lesion: Treatment

Knee cartilage lesion

Anatomy of Articular Cartilage

The hyaline cartilage of the knee has a thickness of 2-6 mm and performs three fundamental functions:

• Absorb compressive loads (up to 6-7 times body weight during running)
• Distribute forces uniformly over the articular surfaces
• Allow almost friction-free gliding between bone surfaces

Cartilage is composed of 65-80% water, a matrix of type II collagen and proteoglycans (aggrecan), and a single cell type: chondrocytes, which represent less than 5% of the total volume.

Why cartilage does not repair itself

• Absence of blood vessels: it does not receive direct nourishment from blood but from synovial fluid by diffusion
• Low cellular turnover: chondrocytes replicate very slowly
• Absence of stem cells in mature cartilage
• Chondral lesions are repaired with fibrocartilage, a tissue of inferior quality compared to the original hyaline cartilage

Causes

Traumatic lesions

• Direct trauma: fall on the knee, impact with another player
• Distortion trauma: often associated with ligamentous (ACL) or meniscal lesions
• Patellar dislocation: lateral dislocation frequently causes chondral lesions of the lateral femoral condyle and the medial facet of the patella

Degenerative lesions

• Early osteoarthritis: progressive thinning and fissuring of the cartilage
• Chronic overload: high-impact sports or work activities
• Limb malalignment: genu varum (medial lesion) or genu valgum (lateral lesion)
• Chronic ligamentous instability: absence of the ACL with repeated stress on the cartilage

Osteochondritis dissecans

A condition in which a fragment of cartilage and subchondral bone separates from the articular surface, more common in young people. It predominantly affects the medial femoral condyle.

Risk factors

Classification (ICRS)

Articular cartilage is avascular hyaline tissue (2-6mm thick) covering bone surfaces, composed of water, collagen, proteoglycans, and chondrocytes, enabling load absorption and frictionless joint movement. The international ICRS (International Cartilage Repair Society) classification divides lesions into grades:

Grade III-IV lesions are the most clinically relevant and those requiring consideration for surgical treatment.

Symptoms

Main symptoms

• Pain: localized to the lesion area, worsens with load and sports activity
• Swelling: recurrent joint effusion, especially after activity
• Stiffness: especially in the morning or after periods of immobility
• Joint locking: if a free intra-articular fragment (loose body) is present
• Giving way: sensation of knee instability
• Crepitus: noise during movement, especially in patellar lesions

Clinical picture by location

Medial femoral condyle (most common site):

• Pain on the inner side of the knee
• Worsening with walking and running
• Swelling after prolonged activity

Lateral femoral condyle:

• Lateral knee pain
• Often associated with ligamentous or meniscal lesions

Patella (articular surface):

• Anterior pain, worsened by stairs, squats, prolonged sitting
• Crepitus on flexion-extension
• Difficulty kneeling

Tibial plateau:

• Less common as an isolated site
• Often secondary to meniscectomy

Diagnosis

Clinical examination

• Anamnesis: mechanism of trauma, type of pain, mechanical symptoms
• Palpation: pain on the joint line
• Specific tests: McMurray test (to rule out meniscal lesion), ligament tests
• Patellar evaluation: patellar grind test, patellar compression
• ROM: generally preserved unless mechanical block

Instrumental examinations

X-ray:

• May be normal in isolated cartilage lesions
• Reduction of joint space in advanced forms
• Rosenberg projection (single-leg standing at 45° flexion) for greater sensitivity

Magnetic Resonance Imaging (MRI):

• First-choice examination for chondral lesions
• Highlights: location, size, depth of the lesion, subchondral bone edema
• Sensitivity 80-95% for grade III-IV lesions
• Specific sequences: T2 fat-sat, proton density, T2 maps

Arthroscopy:

• Diagnostic gold standard: direct evaluation of cartilage
• Allows simultaneous treatment
• Definitive ICRS classification

Conservative Treatment

Indicated for grade I-II lesions, stable lesions, and patients with low functional demands.

Load management

• Temporary reduction of high-impact activities
• Maintenance of low-impact activities: swimming, cycling, elliptical
• Protected loading with crutches in acute post-traumatic phases

Medications and infiltrations

• NSAIDs: pain and inflammation control
• Oral chondroprotectors: glucosamine, chondroitin (limited evidence but safe)
• Hyaluronic acid injections: viscosupplementation, improvement of joint lubrication, 3-5 injections weekly
• PRP (platelet-rich plasma) injections: growth factors that can stimulate repair, promising results
• Cortisone injections: for acute inflammation control (limited use)

Physiotherapy

Phase 1 — Symptom reduction (weeks 1-4):

• Cryotherapy after activity
• Active knee mobilization
• Low-load closed kinetic chain exercises: mini-squats (0-30° flexion)
• Stationary bike without resistance
• Swimming (freestyle legs)

Phase 2 — Strengthening and stabilization (weeks 4-12):

• Quadriceps strengthening: leg press, step-ups, controlled lunges
• Hamstring strengthening: curls, single-leg bridge
• Gluteal strengthening: abduction, clamshell, hip thrust
• Core stability: plank, side plank, bird-dog
• Proprioception: single-leg stance, proprioceptive board

Phase 3 — Return to activity (from 3 months):

• Gradual resumption of running on soft surfaces
• Light plyometric exercises
• Sport-specific activities
• Maintenance of strengthening program

Surgical Treatment

General indications

• Symptomatic grade III-IV lesions
• Failure of conservative treatment
• Intra-articular loose body with mechanical block
• Associated lesions (ACL, meniscus) requiring surgical treatment
• Young and active patient

Surgical techniques

Arthroscopic debridement and chondroplasty:

• Removal of unstable cartilage flaps and smoothing of the surface
• Palliative, does not restore cartilage
• Indicated for small lesions with mechanical symptoms

Microfractures (Steadman):

• Perforation of the exposed subchondral bone to create bleeding and migration of mesenchymal cells
• Formation of a clot that differentiates into fibrocartilage
• Indicated for lesions < 2-4 cm² in patients < 40 years old
• Good short-to-medium term results, deterioration in the long term

Autologous osteochondral transplantation (mosaicplasty):

• Harvesting of osteochondral cylinders from non-weight-bearing areas of the knee and transplanting them into the lesioned area
• Restores true hyaline cartilage
• Indicated for lesions from 1 to 4 cm²
• Limitation: amount of available donor tissue

Donor osteochondral transplantation (allograft):

• Tissue bank graft for large lesions (> 4 cm²)
• Allows treatment of extensive defects

Autologous chondrocyte implantation (ACI/MACI):

• Harvesting of chondrocytes from the patient, culturing in the laboratory, and reimplantation
• MACI: chondrocytes seeded on a collagen membrane
• Indicated for large lesions (> 2-4 cm²) in young patients
• Excellent long-term results, good quality of regenerated tissue
• Two surgeries required (harvesting + reimplantation) in the traditional technique

Associated procedures

• Corrective osteotomy: to correct malalignment (genu varum/valgum) and unload the lesioned compartment
• ACL reconstruction: if instability is present
• Meniscal repair/transplantation: to restore cushioning function

Post-Surgical Rehabilitation

After microfractures

• Weeks 0-6: touch-down weight-bearing (10-15 kg) with crutches, continuous passive motion (CPM), progressive flexion
• Weeks 6-8: progressive partial weight-bearing
• Weeks 8-12: full weight-bearing, light strengthening
• Months 3-6: progressive strengthening, low-impact activities
• Months 6-9: return to sport

After MACI/ACI

• Weeks 0-4: touch-down weight-bearing, passive motion, CPM
• Weeks 4-8: progressive weight-bearing to full
• Months 2-4: strengthening, stationary bike, swimming
• Months 4-9: increasing impact activities
• Months 9-12: return to competitive sport

Common principles

• Rehabilitation is long and gradual to protect the regenerating tissue
• Low-resistance stationary bike is the safest exercise in the initial phases
• Water exercises (hydrokinesiotherapy) are valuable for reduced load
• Return to running generally occurs between the 4th and 6th month
• Return to contact sports requires 9-12 months

Recovery Times

Prevention

• Maintain a healthy body weight: reduces overload on the cartilage
• Strengthen knee musculature (quadriceps, hamstrings, glutes)
• Adequate warm-up before sports activity
• Avoid excessive volume in high-impact sports
• Promptly treat ligamentous and meniscal lesions to prevent secondary cartilage damage
• Correct malalignments when symptomatic

Frequently Asked Questions (FAQ)

Frequently Asked Questions

Can knee cartilage regrow?

Articular cartilage in the knee possesses a limited capacity for self-repair or regrowth due to its avascular nature and low cellular turnover. While certain surgical techniques aim to stimulate the formation of repair tissue, it often differs structurally from native hyaline cartilage.

Does a cartilage lesion always lead to osteoarthritis?

Not all cartilage lesions inevitably progress to osteoarthritis, but they do increase the risk, particularly if left untreated or if the damage is significant. Appropriate management, encompassing conservative or surgical interventions, can help mitigate this risk and preserve joint health.

What is the role of a physical therapist in managing knee cartilage lesions?

A physical therapist is integral to both conservative and post-surgical management of knee cartilage lesions. They develop individualized programs focusing on load management, strengthening, mobility, and rehabilitation to optimize recovery and restore function.

What are the primary treatment approaches for knee cartilage lesions?

Treatment for knee cartilage lesions encompasses both conservative and surgical strategies, tailored to the lesion’s characteristics and severity. Conservative options include load management, medications, infiltrations, and physical therapy, while significant damage often requires surgical intervention.

For a broader overview of related conditions, see our complete guide to knee pain.

Sources and Scientific References

1. Jarecki J et al. (2023). Knee Cartilage Lesion Management-Current Trends in Clinical Practice. J Clin Med. 12. DOI | PubMed
2. Logerstedt DS et al. (2018). Knee Pain and Mobility Impairments: Meniscal and Articular Cartilage Lesions Revision 2018. J Orthop Sports Phys Ther. 48:A1-A50. DOI | PubMed
3. Pujol N et al. (2025). The formal EU-US Meniscus Rehabilitation 2024 Consensus: An ESSKA-AOSSM-AASPT initiative. Part I-Rehabilitation management after meniscus surgery (meniscectomy, repair and reconstruction). Knee Surg Sports Traumatol Arthrosc. 33:3002-3013. DOI | PubMed
4. Sihvonen R et al. (2013). Arthroscopic partial meniscectomy versus sham surgery for a degenerative meniscal tear. N Engl J Med. 369:2515-24. DOI | PubMed
5. Rotini M et al. (2023). Arthroscopic surgery or exercise therapy for degenerative meniscal lesions: a systematic review of systematic reviews. Musculoskelet Surg. 107:127-141. DOI | PubMed