Knee Osteoarthritis (Gonarthrosis): Exercises and Treatment

Knee osteoarthritis (gonarthrosis)

Knee osteoarthritis (or gonarthrosis) is the most common form of osteoarthritis of the lower limbs and one of the leading causes of disability in the adult population. It affects approximately 13% of women and 10% of men over 60, with a prevalence that continues to increase due to population aging and rising obesity.

Gonarthrosis is characterized by the progressive deterioration of the knee’s articular cartilage, resulting in pain, stiffness, and functional limitation. The knee joint is particularly vulnerable because it is a weight-bearing joint that undergoes high loads during standing, walking, and especially climbing and descending stairs.

Scientific evidence shows that physical exercise is the most effective treatment for gonarthrosis, with benefits comparable to and in some cases superior to anti-inflammatory drugs. A structured exercise program, combined with weight management, can reduce pain by 40-60% and significantly delay the need for knee replacement surgery.

Knee Anatomy

The knee is a complex hinge joint formed by the femur, tibia, and patella, located between the hip and ankle, enabling flexion, extension, and rotation movements. The knee is the largest and most complex joint in the human body. It is composed of:

• Three articular compartments:

• Medial femorotibial compartment (inner): the most frequently affected by osteoarthritis

• Lateral femorotibial compartment (outer)

• Patellofemoral compartment (anterior): between the patella and the femur
• Menisci: two fibrocartilage cushions (medial and lateral meniscus) that absorb shock and distribute loads. Meniscus injuries accelerate osteoarthritic degeneration
• Ligaments: anterior cruciate (ACL), posterior cruciate, collateral — stabilize the joint
• Articular cartilage: covers the surfaces of the femur, tibia, and patella, allowing friction-free movement

The knee cartilage undergoes enormous loads: during walking, the knee bears 2-3 times body weight, during stair climbing 3-4 times, during squatting up to 7-8 times. An 80 kg person loads the knee with over 300 kg during a simple squat.

Causes and Risk Factors

Non-Modifiable Factors

• Age: the most important factor. Knee osteoarthritis is rare before 40 and affects over 30% of those over 65
• Female sex: women are affected 1.5-2 times more than men, with a marked increase after menopause
• Genetics: documented family predisposition
• Ethnicity: some populations have a higher risk

Modifiable Factors

• Overweight and obesity: the most important modifiable risk factor. Every excess kg increases the load on the knee by 3-4 kg. Losing 5 kg reduces the load by 15-20 kg with each step
• Previous traumas: articular fractures, ligament injuries (especially ACL), meniscus injuries — increase the risk of osteoarthritis by 4-6 times
• Surgical meniscectomy: removal of the meniscus accelerates cartilage degeneration
• Malalignment: varus knee (bow-legs) or valgus knee (knock-knees) concentrates the load on one compartment
• Heavy labor: jobs requiring kneeling, squatting, lifting weights
• High-impact sports: long-distance running on hard surfaces, soccer (in the long term)
• Muscle weakness: quadriceps weakness reduces shock absorption

Symptoms

Pain

• Location: typically on the medial joint line (inner side of the knee), but can be anterior (patellofemoral compartment) or diffuse
• Start-up pain: pain in the first steps after prolonged sitting, which improves after a few minutes (start-up pain)
• Pain during activity: worsens with prolonged standing, walking, stairs (especially downhill), and squatting
• Pain at rest: in advanced stages, pain is also present at rest and at night
• Weather-related pain: many patients report worsening with cold and humidity

Stiffness

• Morning stiffness: generally lasts less than 30 minutes
• Stiffness after inactivity: the knee “locks up” after periods of inactivity (“gelling” phenomenon)
• Limited flexion: progressive difficulty in fully bending the knee
• Extension deficit: in advanced stages, the knee does not fully straighten

Crepitus

Cracking, crepitus, and grinding sounds during knee movement are very common, especially when climbing stairs or getting up from a chair.

Swelling

Intermittent joint effusion, with a sensation of swelling and warmth in the knee, especially after activity.

Instability

In advanced stages, the knee may “give way” during walking, due to muscle weakness and ligamentous laxity.

Diagnosis

Clinical Examination

• Inspection: varus or valgus deformity, swelling, quadriceps hypotrophy
• Palpation: pain at the joint line, effusion (patellar ballotment)
• Mobility: flexion and extension — often reduced
• Specific tests: patellar tests, meniscal tests, ligamentous tests
• Muscle strength: quadriceps evaluation (often atrophic)
• Gait: gait analysis, assessment of limping

Imaging Diagnostics

• Weight-bearing X-ray: the first-choice examination. It shows joint space narrowing, osteophytes, subchondral sclerosis. The X-ray must be performed standing (weight-bearing) to correctly visualize the joint space
• MRI: indicated to assess the condition of cartilage, menisci, and ligaments
• Full-length standing X-ray of the lower limbs (pangonogram): to assess the mechanical axis of the lower limb (alignment)

Conservative Treatment

OARSI, EULAR, and ACR guidelines recommend conservative treatment as the first approach, with three fundamental pillars.

1. Physical Exercise

The most effective treatment for gonarthrosis. Scientific evidence is strong: exercise reduces pain and improves function to a comparable extent as NSAIDs, with lasting effects and no side effects.

2. Weight Management

Losing 5-10% of body weight is sufficient to achieve a clinically significant improvement in symptoms. The combination of diet and exercise is more effective than either intervention alone.

3. Education

Understanding the disease, self-management strategies, the importance of exercise, and when to seek help.

Medications

• Paracetamol: first-choice analgesic
• Oral NSAIDs (ibuprofen, naproxen): for flare-ups, for limited periods
• Topical NSAIDs (diclofenac gel): effective and with fewer side effects than oral NSAIDs — recommended as first-choice pharmacological treatment
• Intra-articular corticosteroid injections: effective for flare-ups with effusion (max 3-4 per year)
• Hyaluronic acid injections: viscosupplementation — moderate evidence, may improve joint lubrication

Physiotherapy

• Therapeutic exercises: the core of the treatment
• Manual therapy: patellar and femorotibial joint mobilization
• Patellar taping: can reduce anterior knee pain
• Orthotics and insoles: if malalignment is present
• Assistive devices: walking stick (in the hand opposite the painful knee) to reduce load

Exercises for Gonarthrosis

The exercise program should be performed at least 3 times a week, ideally daily. Your doctor or physical therapist will adapt the program to your specific situation.

Quadriceps Strengthening

The quadriceps is the most important muscle for protecting the osteoarthritic knee.

Isometric quadriceps contraction (quad set)

[IMAGE: Person lying supine with legs extended. A rolled towel is placed under the knee. The quadriceps contracts, flattening the knee against the towel, the patella moves upwards. The contraction is held for 10 seconds. Lateral view with detail of quadriceps contraction and patellar movement.]

Seated knee extension (modified SLR)

[IMAGE: Person sitting on a chair with a straight back. The knee slowly extends to full extension, holding the position for 5 seconds. The foot is in dorsiflexion (toes pointing upwards). Lateral view with detail of the extension angle and foot position.]

Wall mini squat

[IMAGE: Person standing with their back against a wall, feet 30 cm forward and shoulder-width apart. The knees slowly bend to about 45 degrees (not beyond 90), then return to standing. The back remains in contact with the wall. Lateral view with detail of the knee angle.]

Gluteal and Hamstring Strengthening

Glute bridge

[IMAGE: Person lying supine with knees bent and feet on the floor. The pelvis lifts to form a straight line from shoulders to knees. Arms are along the sides. Lateral view highlighting the alignment.]

Clamshell (hip abduction)

[IMAGE: Person lying on their side with knees bent at 45 degrees and feet stacked. The upper knee lifts while keeping the feet in contact, like an opening shell. Frontal view showing the knee opening angle.]

Mobilization

Seated knee flexion and extension (pendulum)

[IMAGE: Person sitting on a high chair (or edge of a table) with legs hanging freely. The knee slowly swings in flexion and extension, using gravity. Lateral view showing the pendulum movement of the leg.]

Heel slide

[IMAGE: Person lying supine on a mat. The heel slides on the mat, slowly bending the knee (flessione), then returns to the extended position (extension). A towel under the heel facilitates sliding. Lateral view with detail of heel movement.]

Stretching

Quadriceps stretch

[IMAGE: Person standing, grasping the ankle of the painful side behind them, bringing the heel towards the glute. The knee remains close to the other knee. The other hand rests on a support for balance. Lateral view with detail of the knee flexion angle.]

Hamstring stretch

[IMAGE: Person sitting on the edge of a chair with one leg extended forward, heel on the ground and toes pointing upwards. The torso leans forward, keeping the back straight, until a stretch is felt in the back of the thigh. Lateral view with detail of torso inclination.]

Aerobic Activity

• Walking: 30 minutes, 5 times a week
• Cycling/stationary bike: low impact on the knee, excellent for mobility
• Swimming and aquagym: water supports body weight
• Elliptical: low impact, good cardiovascular workout

When Is Knee Replacement Necessary?

Knee replacement surgery is indicated when:

• Pain is severe and does not respond to at least 3-6 months of conservative treatment
• Functional limitation significantly compromises quality of life
• X-ray shows advanced osteoarthritis (Kellgren-Lawrence grade 3-4)
• Night pain is intractable

Total knee replacement is a procedure with high satisfaction rates (85-90%). The average lifespan is 15-20 years.

Timeline and Prognosis

Prevention

• Maintain a healthy weight: the most important preventive factor
• Quadriceps strengthening: protects cartilage from impacts
• Regular physical activity: keeps cartilage nourished
• Avoid excessive impact: alternate running with low-impact activities
• Treat injuries: properly treated meniscal and ligamentous injuries reduce the risk of secondary osteoarthritis
• Appropriate footwear: cushioned shoes, insoles if necessary

For more information, consult the Complete Guide to Knee Pain.

Frequently Asked Questions (FAQ)

Frequently Asked Questions

How does physical exercise contribute to the management of knee osteoarthritis?

Regular physical exercise is a cornerstone of conservative treatment for knee osteoarthritis. It significantly reduces pain, improves joint function, and strengthens the muscles supporting the knee, thereby enhancing stability and reducing stress on the joint.

What is the significance of weight management in treating knee osteoarthritis?

Weight management plays a crucial role in alleviating symptoms and slowing the progression of knee osteoarthritis. Losing even a small amount of weight substantially reduces the load on the knee joint, which can lead to a significant reduction in pain and may delay the need for surgical intervention.

What specific types of exercises are generally recommended for individuals with knee osteoarthritis?

Recommended exercises typically include quadriceps, gluteal, and hamstring strengthening to support the knee joint. Mobilization and stretching exercises are also important for maintaining range of motion, alongside aerobic activities to improve overall cardiovascular health and endurance.

How can a physical therapist support individuals with knee osteoarthritis?

A physical therapist can provide invaluable support by developing individualized exercise programs tailored to specific needs and capabilities. They educate individuals on proper movement mechanics, pain management strategies, and techniques to improve strength, flexibility, and overall functional mobility.

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

Sources and Scientific References

1. Kan HS et al. (2019). Non-surgical treatment of knee osteoarthritis. Hong Kong Med J. 25:127-133. DOI | PubMed
2. Dantas LO et al. (2021). Knee osteoarthritis: key treatments and implications for physical therapy. Braz J Phys Ther. 25:135-146. DOI | PubMed
3. Michael JW et al. (2010). The epidemiology, etiology, diagnosis, and treatment of osteoarthritis of the knee. Dtsch Arztebl Int. 107:152-62. DOI | PubMed
4. van Doormaal MCM et al. (2020). A clinical practice guideline for physical therapy in patients with hip or knee osteoarthritis. Musculoskeletal Care. 18:575-595. DOI | PubMed
5. Tore NG et al. (2023). The quality of physiotherapy and rehabilitation program and the effect of telerehabilitation on patients with knee osteoarthritis. Clin Rheumatol. 42:903-915. DOI | PubMed