Cartilage damage in the knee

Anatomy: Cartilage and sliding mechanics in the knee

The knee joint consists of the thigh bone (femur), shinbone (tibia) and kneecap (patella). The joint surfaces are covered with hyaline cartilage - a smooth, elastic tissue that absorbs shock and enables low-friction gliding. The menisci are located between the femur and tibia as additional buffers. The synovial membrane (synovia) produces synovial fluid that nourishes and lubricates the cartilage.

• Hyaline cartilage: smooth, elastic to pressure, low ability to regenerate
• Menisci: load distribution, shock absorption
• Synovia: nourishes the cartilage, reduces friction
• Ligament system/muscles: Stability and guidance of the joint

Cartilage has only a few cells and no blood vessels. Therefore, it heals much more slowly after damage than other tissues. Good joint mechanics, sufficient movement and healthy muscles are crucial for the care of the cartilage.

Causes and risk factors

Cartilage defects can occur acutely or gradually. Often several factors work together. An early diagnosis helps to address risk factors that can be influenced.

• Trauma: twisting (e.g. during sports), falls, accompanying bony injuries
• Instabilities: e.g. B. Cruciate ligament rupture, insufficient collateral ligaments
• Misalignments: O-/X-leg (varus/valgus) with unevenly distributed load
• Overload: high jumping and impact loads, abrupt increase in training
• Meniscus damage: reduced shock absorption
• Overweight: increased joint forces in everyday life
• Muscular imbalances and limited mobility
• Rare: metabolic/circulatory disorders, osteochondrosis dissecans

Symptoms: How do I recognize cartilage damage?

• Stress-dependent pain, start-up pain
• Swelling/effusion, feeling of tension
• Crepitation (rubbing noise/feeling), occasionally feelings of pinching
• Pain when bending/stretching, climbing stairs, squatting
• For larger defects: blockages, buckling, limited extension/flexion

The localization can provide clues: anterior knee pain is more likely to indicate patellofemoral involvement (knee cap bearing), while pain on the inside or outside is more likely to indicate femorotibial defects.

Classification and forms of cartilage damage

Cartilage injuries differ according to depth (severity), extent, location and accompanying factors (malposition, instability, meniscus status). Usual severity levels are based on ICRS/Outerbridge.

• Chondral defects: only cartilage affected
• Osteochondral defects: Cartilage and underlying bone affected
• Location: femorotibial (inside/outside), patellofemoral (kneecap/sliding bearing)
• Accompanying problems: axial misalignment, ligament insufficiency, loss of meniscus

Diagnostics: This is how we proceed

Diagnostics includes anamnesis, physical examination and imaging procedures. We evaluate stress, previous injuries and the individual symptoms. It is important to assess the entire joint function - not just the defect.

• Clinical: Gait, axis, mobility, pressure/gliding and compression tests, signs of effusion
• X-ray: assessment of the joint space width, axis (whole leg image), accompanying bony findings
• MRI: Assessment of cartilage, menisci, ligaments, bone marrow edema - standard when cartilage damage is suspected
• Sonography: Evidence of effusions/inflammation of the synovium
• Rare: diagnostic arthroscopy if the findings are unclear and symptoms persist

The findings are compared with activity level, age, previous illnesses and goals (everyday life, work, sport). This creates an individual treatment plan.

Conservative therapy: The first and most important step

Most cartilage damage can initially be treated without surgery. The aim is to reduce pain, reduce inflammation, optimize joint guidance and increase stress in a measured manner. A structured, consistently implemented plan is crucial.

• Activity adjustment: temporarily reduce impact and twisting loads, gradually return to work
• Physiotherapy: Strengthen hip and knee muscles (quadriceps, gluteal muscles), improve mobility/patellar gliding, neuromuscular training
• Weight management: Even small weight reductions significantly reduce knee joint forces
• Inflammation management: Cooling in acute phases, time-limited NSAIDs after medical consultation
• Aids: taping, patella-guiding bandages, if necessary temporary relief orthoses if the deformity is severe
• Everyday strategies: stairs in doses, avoiding deep squatting, cycling and swimming as alternatives that are gentle on the joints

Injection therapies may be considered in select situations. They do not replace training and load management, but they can reduce complaints:

• Hyaluronic acid: viscoelastic support of the gliding function, evidence varies depending on the situation
• PRP (platelet-rich plasma): the body's own growth factors; Use for cartilage pain is discussed, data is heterogeneous
• Corticoids: possible in individual acute inflammatory phases, rather short-term effect

We only use regenerative procedures after clear indications, information about benefits and limitations and in combination with a load-adaptive rehabilitation concept.

Surgical options: When does an intervention make sense?

Operations are considered if, despite consistent conservative therapy, persistent, stressful symptoms persist and the type of defect is suitable for this. The choice of procedure depends on size, depth, location, age, activity, axis, stability and meniscus status.

• Arthroscopic smoothing/debridement: symptom-oriented smoothing of frayed edges in the event of mechanical irritation
• Bone marrow stimulation (microfracture/needling): Promotion of replacement cartilage (fibrocartilage) in small, circumscribed defects
• AMIC/matrix-supported procedure: combination of bone marrow stimulation and membrane for defect filling
• Osteochondral transfer (OATS/mosaicplasty): Cylindrical transplants from less stressed areas for focal defects
• Autologous chondrocyte transplantation (ACT/MACI): two-stage procedure for larger, localized chondral defects
• Axial and accompanying interventions: corrective osteotomy for varus/valgus, meniscus reconstruction/replacement, ligament stabilization - often crucial for long-term success

No method can reliably “heal” damaged hyaline cartilage. The aim is to alleviate symptoms and improve function. Realistic expectations and consistent rehabilitation are essential success factors.

Depending on the technique, rehabilitation after surgical procedures includes passive-assistive movements, partial weight-bearing, gradual strength building and sport-specific training. Depending on the procedure, time frames range from weeks to several months.

Course and prognosis

The natural healing ability of cartilage is limited. Nevertheless, the symptoms can often be significantly improved through targeted training, weight management, load control and – selectively – injections. Larger, deep defects and persistent accompanying factors (e.g. misalignment, instability) increase the risk of developing osteoarthritis.

• Favorable: small, circumscribed defects, stable joint guidance, good muscle balance
• Unfavorable: extensive defects, loss of meniscus, axis misalignment, constant overload

Regular follow-up checks are important in order to adapt therapy components and recognize warning signs early.

Self-help: What you can do yourself

• Exercise yes, shock load no: cycling, swimming, elliptical trainer; Dose jumping/sprinting sports
• Strength plus mobility: 2-3x/week exercises for quadriceps, hips, core; Stretching the front thigh muscles
• Keep an eye on weight: realistic, small steps bring noticeable relief
• Adapt to everyday life: carry loads close to your body, plan breaks, avoid kneeling/squatting for long periods of time
• Acute measures: Cooling if there is a tendency to effusion, and if there is irritation, temporarily reduce stress

Arrangements with physiotherapy help to adapt the training to the daily form and irritation conditions. Take pain seriously as a warning signal - train for a short period of time instead of taking a complete break.

When should I seek medical advice?

• Persistent pain or swelling despite rest for several weeks
• Blockages, feelings of pinching or buckling
• Acute severe pain/swelling after accident
• Fever, redness or warm joint
• Increasing restrictions in everyday life or during sports

Early clarification makes it possible to break cycles of irritation and avoid consequential damage.

Related diagnoses and differential diagnoses

Cartilage damage is part of a spectrum. Depending on the location and accompanying symptoms, further diagnoses may be considered, which we examine in a differentiated manner:

• Gonarthrosis: advanced joint wear with cartilage loss
• Patellofemoral arthrosis or chondropathia patellae: front knee pain, discomfort when climbing stairs/bending
• Osteochondrosis dissecans: circumscribed osteochondral lesion, common in younger people
• Synovitis/irritable effusion: inflammatory activity of the joint mucosa
• Plica mediopatellaris syndrome: mucosal fold in the joint that can cause mechanical irritation

Your path to individual therapy in Hamburg

In our practice at Dorotheenstrasse 48, 22301 Hamburg, you will receive a structured diagnosis and a clear, everyday treatment plan. We start conservatively, closely integrate physiotherapy and transparently discuss the advantages and disadvantages of further procedures. Operational options are – if appropriate – planned with experienced partners.