Knee Cartilage Damage (Chondral Injury)
Knee cartilage damage (chondral injury) is a defect or loss of the smooth articular cartilage that lines the knee joint surfaces. It causes knee pain, swelling, and locking and, if untreated, can progress to full osteoarthritis. Mr Shakir Hussain, Consultant Orthopaedic Surgeon at the Royal Orthopaedic Hospital Birmingham, assesses and manages knee cartilage damage, including knee replacement for patients who develop advanced arthritis.
What is knee cartilage damage?
Articular cartilage is the smooth, white tissue that coats the ends of the bones inside the knee joint. It acts as a shock absorber, distributes load evenly across the joint, and allows virtually frictionless movement. When this cartilage is damaged, either by injury or progressive degeneration, pain, swelling, and mechanical symptoms follow, and the joint becomes vulnerable to the development of osteoarthritis over time.
The knee has three articular surfaces that can sustain cartilage damage: the medial femoral condyle (inner part of the thighbone), the lateral femoral condyle (outer part of the thighbone), and the patella (kneecap). The cartilage on the tibial plateau below can also be affected.
Articular (hyaline) cartilage is a highly specialised tissue. Unlike most other tissues in the body, it has no blood supply of its own and is nourished by the surrounding joint fluid. This means it has very limited capacity for self-repair: once damaged, a focal defect will not close or fill with healthy hyaline cartilage without surgical intervention.
There are two broad categories of knee cartilage damage. Traumatic chondral injuries occur acutely following a significant knee injury, often alongside ligament or meniscal tears. Degenerative chondral loss occurs gradually as part of the osteoarthritis process, typically in older patients. Both can cause significant symptoms, and both can ultimately lead to end-stage osteoarthritis requiring knee replacement if not adequately managed.
What does knee cartilage damage feel like?
Activity-related pain inside the knee that may be sharp or aching, worsened by twisting and impact activities. Swelling after exercise is common. A catching, locking, or clicking sensation suggests a loose cartilage fragment. Symptoms often fluctuate and may be mild for years before progressing to more persistent pain.
The symptoms of knee cartilage damage vary depending on the size, location, and depth of the defect. Small, superficial lesions may cause no symptoms at all and be found incidentally on MRI. Larger or full-thickness defects tend to produce more consistent and disabling symptoms.
Activity-related knee pain
Pain is typically brought on by loading activities such as walking, running, and climbing stairs, and may be localised to the affected compartment. It often eases with rest, at least in the early stages.
Swelling after activity
Mechanical irritation from a cartilage defect causes the synovium to produce excess fluid, resulting in a swollen, puffy knee after physical activity. Persistent swelling at rest signals advancing disease.
Locking or catching
A loose cartilage fragment that has detached from the joint surface can become trapped between the joint surfaces, causing the knee to lock briefly or produce a sharp catching sensation during movement.
Joint-line tenderness
Pressure over the joint line of the affected compartment is typically painful on clinical examination, helping to localise the damaged area before imaging.
Crepitus (grinding)
A grinding or grating sensation felt during knee movement indicates that roughened cartilage surfaces, or exposed bone, are in contact with each other during the normal arc of motion.
Reduced range of motion
Significant cartilage loss or a large loose body can restrict the range of movement available in the knee, particularly full flexion (bending). This is more common in advanced or long-standing cases.
What causes knee cartilage damage?
Knee cartilage damage results from acute injury (a twisting fall, impact, or sports collision) or from gradual degenerative thinning associated with age, obesity, malalignment, and prior meniscal surgery. Cartilage damage after meniscal removal is a well-recognised long-term complication, as the meniscus normally acts as the primary shock absorber protecting the articular surface.
The main causes and contributing factors include:
- Acute knee injury. A sudden twisting force, direct blow, or landing impact can shear or fracture articular cartilage, sometimes with no other structural damage visible on initial imaging. Osteochondral fractures (affecting both cartilage and underlying bone) can occur in younger patients following sports trauma.
- Prior meniscal injury or meniscectomy. The menisci absorb up to 50 per cent of compressive load across the knee. Removal of meniscal tissue, whether partial or total, exposes the cartilage beneath to abnormally high loads, accelerating wear. This is one of the most common causes of chondral damage in middle-aged patients.
- Age-related degeneration. Articular cartilage thins with age even in the absence of injury, as the chondrocytes (cartilage cells) that maintain the matrix become less active and fewer in number.
- Obesity (BMI over 29). Each extra stone of body weight increases the load through the knee with every step, accelerating cartilage wear at a rate disproportionate to body weight alone.
- Malalignment (varus or valgus). A bow-legged or knock-kneed deformity concentrates force on one compartment of the knee, leading to localised cartilage loss in the overloaded area. Correcting alignment through osteotomy can slow this progression in selected younger patients.
- Repetitive high-impact loading. Years of high-impact sport or physically demanding occupational activity increase the cumulative load on the cartilage beyond its repair capacity.
How is knee cartilage damage diagnosed?
MRI is the investigation of choice for knee cartilage damage, showing the size, depth, and precise location of cartilage defects. The ICRS (International Cartilage Repair Society) grading system classifies defects from Grade 1 (softening only) to Grade 4 (full-thickness loss with exposed bone). X-rays may be entirely normal in early or isolated cartilage damage.
Clinical assessment begins with a careful history of the injury or onset, the pattern of symptoms, and any prior knee surgery. Examination identifies the affected compartment through joint-line tenderness, effusion, and crepitus. Imaging confirms the diagnosis:
- MRI. The primary investigation. Dedicated cartilage-sensitive sequences map defect size, depth, and location with high accuracy. MRI also assesses the menisci, ligaments, and subchondral bone, which may be co-affected.
- ICRS Grading. Grade 1: cartilage softening or blistering with intact surface. Grade 2: superficial defect less than 50 per cent of cartilage depth. Grade 3: deep defect more than 50 per cent of cartilage depth but not through to bone. Grade 4: full-thickness loss exposing subchondral bone.
- Weight-bearing X-rays. Essential to assess joint-space narrowing when degenerative disease is suspected. Normal in early isolated chondral injury but show narrowing when full-thickness loss is extensive.
- CT arthrogram. Used in selected cases where MRI is contraindicated or where precise bone stock assessment is needed before cartilage repair surgery.
Can knee cartilage damage be managed without surgery?
Yes, particularly for smaller or more superficial defects and for patients with mild symptoms. Physiotherapy to strengthen the muscles protecting the joint, weight loss, and activity modification can reduce pain and slow progression. Anti-inflammatory medication and intra-articular injections can help manage flares. Surgery is considered when symptoms are substantial and do not respond to conservative care.
Conservative management aims to reduce pain, protect the remaining cartilage, and delay or avoid surgical intervention where possible:
- Physiotherapy. Quadriceps, hamstring, and hip abductor strengthening reduces the dynamic load transmitted through the damaged cartilage with each step and helps stabilise the joint during activity.
- Weight management. Reducing body weight by even 5 to 10 per cent meaningfully reduces cartilage loading and slows the rate of wear.
- Activity modification. Replacing high-impact activities (running, jumping) with low-impact alternatives (swimming, cycling) reduces cartilage loading without sacrificing cardiovascular fitness.
- Anti-inflammatory medication. Topical or oral NSAIDs can reduce pain and swelling during flares, though they do not modify the underlying cartilage defect.
- Intra-articular injections. Corticosteroid or hyaluronic acid injections can provide 4 to 12 weeks of symptom relief, acting as a bridge before definitive treatment or to facilitate a physiotherapy programme.
When does cartilage damage require surgery?
When cartilage loss is extensive, the joint develops full-thickness arthritis, and symptoms substantially affect daily life despite conservative or cartilage-specific treatment, knee replacement becomes appropriate. Partial knee replacement suits single-compartment disease; total knee replacement is needed for multi-compartment involvement. For younger patients with focal defects, cartilage repair techniques may be an option before arthritis becomes generalised.
The appropriate surgical treatment depends on the patient's age, the size and location of the defect, the presence or absence of surrounding arthritis, and the degree of functional impairment:
Knee Replacement
When cartilage damage has progressed to full-thickness osteoarthritis affecting one or more compartments, knee replacement is the most reliable and durable treatment. Partial replacement is suitable for single-compartment disease; total replacement is required when multiple compartments are involved. Mr Hussain offers both with robotic assistance.
- Partial replacement for isolated single-compartment arthritis
- Total replacement for multi-compartment or whole-joint disease
- Robotic-assisted (MAKO, ROSA, CORI) for precise implant positioning
- Modern implants with a 20 to 25 year expected lifespan
- Most patients mobilising the same day as surgery
Cartilage Repair Techniques
For younger patients with isolated, full-thickness focal defects surrounded by healthy cartilage, cartilage repair techniques may be considered before arthritis becomes generalised. These include microfracture, autologous chondrocyte implantation (ACI), and AMIC procedures. These are performed by specialist cartilage preservation surgeons and are outside the scope of Mr Hussain's practice, but he can advise on the appropriate pathway for younger patients.
- Microfracture: stimulates fibrocartilage repair from bone marrow cells
- ACI: transplant of cultured cartilage cells into the defect
- AMIC: combination of microfracture and a collagen membrane scaffold
- Best results in patients under 45 with defects under 4 sq cm
- Longer recovery than knee replacement (6 to 18 months)
What are the outcomes after knee replacement for cartilage damage?
When cartilage damage has progressed to full arthritis and knee replacement is performed, outcomes are excellent. National Joint Registry data shows approximately 90 per cent of total knee replacements are still functioning at 15 years. Patient satisfaction is approximately 80 to 85 per cent. Early intervention to address cartilage damage, before generalised arthritis develops, may avoid or delay the need for replacement in selected patients.
The key determinant of outcome is matching the right treatment to the right patient at the right stage of the disease. For patients who have progressed to generalised osteoarthritis, knee replacement, performed with robotic guidance, provides the most predictable and durable result. Mr Hussain holds certifications on three robotic platforms (MAKO, ROSA, and CORI), allowing personalised implant positioning for each patient's anatomy.
Expertise in knee cartilage treatment in Birmingham
Consultant at the Royal Orthopaedic Hospital
Mr Hussain practises at the Royal Orthopaedic Hospital Birmingham, one of the largest specialist orthopaedic hospitals in Europe, alongside Priory Hospital Edgbaston and Harborne Hospital.
3,000+ arthroplasty cases
From a total of more than 5,000 procedures performed, giving the operative volume and case complexity required for consistently excellent outcomes. Read more about Mr Hussain's training and background.
MAKO, ROSA, and CORI robotic certifications
Mr Hussain holds certifications on all three major robotic knee replacement platforms, allowing robotic-assisted surgery to be offered to all suitable patients regardless of which platform is available at their chosen hospital.
Complex revision surgery expertise
Mr Hussain performs revision knee replacement for patients whose primary replacement has failed, including for infection, loosening, and instability. See revision knee surgery for more information.
Doctify Outstanding Patient Experience 2024, 2025, and 2026
Awarded in three consecutive years, recognising consistently high patient-reported outcomes and communication throughout the surgical journey.
4.98 out of 5 from verified reviews on Doctify. Outstanding Patient Experience Award 2024, 2025, and 2026.
Frequently asked questions about knee cartilage damage
For more questions about surgery, recovery, fees, and what to expect, see the full frequently asked questions page or read recent patient testimonials.