The decision between minimally invasive arthroscopy and knee replacement presents a challenge for many patients and doctors. While arthroscopy is considered a gentle procedure, knee replacement promises a lasting solution for advanced damage. But when is each method truly appropriate? In this comprehensive guide, we examine the differences between isolated meniscus tears and degenerative damage caused by osteoarthritis, offer treatment recommendations for various patient groups, and explain why arthroscopy is often unsuccessful in cases of existing osteoarthritis. We also discuss partial joint replacement, such as unicompartmental knee arthroplasty, in detail and show when it represents an effective alternative to arthroscopy or total knee replacement.

1. Anatomy and function of the knee joint

To better understand the various treatment options, it's helpful to first look at the anatomy of the knee. The knee is one of the largest and most complex joints in the human body. It consists of:

• Femur (thigh bone)
• Tibia (shinbone)
• Patella (kneecap)
• Menisci – two crescent-shaped cartilage discs that act as shock absorbers
• Ligaments (cruciate and collateral ligaments) for stabilization
• Articular cartilage , which enables smooth movement

Damage to any of these components can cause pain, restricted movement, and instability. Depending on the cause of the symptoms, different therapies are available.

Difference between isolated meniscus injuries and degenerative damage due to osteoarthritis

The knee joint is one of the most stressed joints in the human body and is therefore prone to various injuries and degenerative changes.

Isolated meniscus injuries:

The meniscus acts as a shock absorber between the thighbone and shinbone. Acute injuries, such as those sustained during sports, can lead to tears. Typical symptoms include sudden pain, swelling, and restricted movement. In such cases, arthroscopy may be a useful procedure to repair the tear or remove the damaged portion.

Degenerative damage caused by osteoarthritis:

Osteoarthritis is a chronic, progressive disease in which the articular cartilage is gradually broken down. Causes can include overuse, misalignment, or genetic factors. Symptoms include pain, stiffness, and limited mobility. Unlike acute injuries, osteoarthritis develops over years.

2. Isolated meniscus injuries and degenerative damage: The most important differences

2.1 Isolated meniscus injuries

Isolated meniscus injuries often result from sports accidents or abrupt movements. The meniscus can tear, leading to sudden pain, swelling, and locking in the knee. Typical symptoms include:

• Sharp pain, especially during twisting movements
• A feeling that the knee is "catching" or blocked
• Swelling after exertion

👉 Treatment option: In younger patients or with fresh tears, arthroscopic meniscus repair may be useful to preserve the meniscus.

2.2 Degenerative damage caused by osteoarthritis

Osteoarthritis is a gradual, progressive wear and tear of the articular cartilage. Typical symptoms include:

• Start-up pain
• Pain during exertion
• Morning stiffness
• Crunching in the knee

👉 Treatment options: Conservative measures (physiotherapy, painkillers, hyaluronic acid) can slow the progression. However, in advanced cases of osteoarthritis, joint replacement is often unavoidable.

Treatment options: Isolated injuries vs. degenerative damage

Isolated meniscus injuries:

• Acute conditions: In cases of sudden injuries without prior knee problems, arthroscopy may be a suitable option. This minimally invasive procedure allows for a rapid restoration of function.
• Young patients: In young, active individuals, arthroscopic repair is often preferred to preserve natural joint function.

Degenerative damage caused by osteoarthritis:

• Chronic conditions: For persistent pain and advanced osteoarthritis, conservative measures such as physiotherapy, pain medication and weight reduction are the first choice.
• Older patients: In older individuals with significant limitations, joint replacement, such as a partial knee replacement, may be considered.

3. When is knee arthroscopy advisable?

Knee arthroscopy was long a common procedure for osteoarthritis. However, studies show that it offers no long-term benefit in cases of degenerative changes. Today, arthroscopy is primarily used for:

• Fresh meniscus tears (especially in younger patients)
• Loose bodies in the joint (e.g., cartilage fragments that block the joint)
• Knee joint effusion of unknown cause

👉 for osteoarthritis ! The cartilage damage persists, and the symptoms usually return.

Arthroscopy in cases of existing osteoarthritis: Why is it often ineffective?

Studies have shown that arthroscopy offers no long-term benefit for patients with knee osteoarthritis. Neither pain nor joint function is sustainably improved. Therefore, this procedure is no longer recommended as a standard treatment for existing osteoarthritis.

Partial knee replacement: Unicompartmental knee replacement as an effective solution

In cases of unilateral osteoarthritis affecting only part of the knee joint, a partial knee replacement can be a less invasive alternative to total knee replacement. This procedure replaces only the affected section of the joint, leading to faster rehabilitation and a more natural feeling of movement. This is only possible if the knee ligaments are stable and there are no malalignments.

4. Knee replacement: full vs. partial joint replacement

In advanced stages of osteoarthritis, a knee replacement offers a permanent solution. There are two main types:

4.1 Total knee endoprosthesis (knee TEP)

This procedure involves replacing the entire knee joint. It is recommended for:

• Complete cartilage destruction
• Pronounced malposition (X-/O-leg)
• Pain in multiple parts of the knee

👉 Advantage: Pain relief, long-term solution

👉 Disadvantage: Longer rehabilitation time, more bone substance has to be removed

4.2 Partial denture (unicompartmental denture)

A partial knee replacement only replaces the damaged part of the knee – usually the inner side. Requirements:

• Only unilateral osteoarthritis
• Stable bands
• No pronounced malpositions

👉 Advantage: Less bone removal, faster recovery, natural feeling of movement

👉 Disadvantage: Not suitable for advanced osteoarthritis in multiple knee sections

5. Which therapy for whom? A detailed guide

The choice between knee arthroscopy, partial knee replacement (e.g., unicompartmental knee arthroplasty), or total knee replacement depends on various factors. Here is a detailed explanation:

5.1 Isolated meniscus injuries

Typical patient: Younger, athletically active people or middle-aged people with sudden, exertion-related pain after a trauma.

Recommended therapy:

• Knee arthroscopy: In cases of acute, clearly defined meniscus tears without cartilage damage, minimally invasive arthroscopy can be a useful option. The tear is either sutured (if the location is favorable) or the damaged portion of the meniscus is removed (partial resection). It is important to preserve as much meniscus tissue as possible to minimize the risk of developing osteoarthritis later in life.
• Rehabilitation: A return to sports is possible after just a few weeks, especially after partial resections. A longer period of rest is recommended after sutures.

Prognosis: Good for isolated tears without additional damage. Caution is advised in cases of degenerative changes – arthroscopy is usually not very promising in these cases.

5.2 Degenerative damage and osteoarthritis

Typical patient: Older patients (>50 years), individuals with persistent pain, increasing limitations in movement and X-ray findings showing cartilage wear.

Recommended therapy:

• Knee arthroscopy: Rarely useful in this case. Studies show that arthroscopy usually does not bring about long-term improvement in osteoarthritis. It is therefore no longer routinely recommended.
• Partial knee replacement (unicompartmental knee replacement): If only one compartment of the knee (usually the inner side) is affected, a unicompartmental knee replacement can be a good solution. The healthy part of the joint is preserved, allowing for faster rehabilitation and a more natural feeling of movement.
• Knee replacement: In cases of advanced osteoarthritis affecting multiple compartments, total knee replacement remains the last option. This involves replacing the entire joint.

Rehabilitation:

• Sledge prosthesis: Patients can often walk well again after a few weeks, many even without walking aids.
• Knee replacement: Full recovery often takes several months, but offers long-term pain relief and improved function.

Prognosis: Improved mobility and pain relief when indicated. In particular, partial knee replacement offers good long-term results in cases of localized osteoarthritis.

5.3 Acute vs. long-lasting symptoms

• Acute pain after trauma: A thorough diagnosis should be performed first (MRI, X-ray). Arthroscopy can be helpful in cases of isolated meniscal tears or loose bodies in the joint.
• Persistent symptoms: In cases of chronic pain, especially with existing osteoarthritis, arthroscopy is usually no longer indicated. In these cases, joint-preserving measures such as partial joint replacement or, in advanced osteoarthritis, knee replacement are more suitable.

5.4 Younger vs. older patients

• Younger patients: Here, joint preservation is the primary goal. Arthroscopy for isolated injuries or a joint-preserving partial knee replacement are preferred to postpone a later total knee replacement.
• Older patients: In older age and with advanced osteoarthritis, a knee replacement offers long-term pain relief and improved mobility. A partial knee replacement also remains an option if the osteoarthritis is limited to one area.

5.5 Summary: The path to the right therapy decision

Choosing the right treatment depends on many individual factors – age, activity level, pain intensity, and joint condition. Isolated arthroscopy is usually no longer advisable in cases of degenerative damage. Partial replacements, such as unicompartmental knee replacement, often offer a gentler alternative with faster rehabilitation and a more natural feel. For advanced osteoarthritis, total knee replacement remains the reliable option for long-term pain relief.

An individual consultation with an experienced orthopedist is essential to select the appropriate therapy and avoid overtreatment.

Conclusion

Choosing the right therapy for knee problems depends on the type of injury or condition, the duration of the symptoms, and the patient's age. While arthroscopy can be beneficial for isolated meniscus tears, it is often unsuccessful in cases of existing osteoarthritis. In such cases, a partial joint replacement, such as a unicompartmental knee replacement, can be an effective solution to improve the patient's quality of life.

Arthroscopy or prosthesis?

Arthroscopy is particularly suitable for acute meniscus injuries – but not for osteoarthritis. In cases of degenerative knee changes, partial prostheses such as unicompartmental knee replacement offer a good alternative to total knee replacement if only one section of the knee is affected.

A thorough diagnosis and individual consultation by experienced orthopedic surgeons is crucial to finding the best possible treatment.

👉 Question for you: Do you have knee problems and are unsure which therapy is right for you? Feel free to schedule a consultation!