Last updated: 2026-07-24
What Knee Osteoarthritis and Cartilage Wear Actually Mean
Even if knee osteoarthritis causes pain and limits your activities, there is no need to rush into surgery simply because you have been told that your cartilage has worn down. Surgery should be considered if walking and sleeping remain difficult even after stepwise treatment with exercise, weight management, medication, and injections.
Knee osteoarthritis does not affect only one area of cartilage. As the cartilage covering the joint surfaces thins and cracks, the bone underneath hardens or changes shape. The synovium lining the joint may also become inflamed. The joint capsule, ligaments, and thigh muscles are also affected as they bear the altered load. It is a chronic disease in which the entire joint changes over a long period.(Jang Sunhee et al., 2021)
If an X-ray shows narrowing of the joint space, the cartilage may have become thinner. Osteophytes—bone growths resembling spurs—may be visible along the edges of the bones, and the bone beneath the joint surface may appear denser. The amount of wear seen on imaging does not always match the severity of the pain. Some patients continue their daily activities even when the cartilage has become considerably thinner, while others experience severe pain every time they walk down stairs despite having only early changes.
Changes in the Cartilage, Subchondral Bone, and Synovium Work Together to Cause Pain
Cartilage itself has almost no nerves that sense pain. This is why cartilage wear alone cannot be identified as the cause of knee pain.
Pain may occur when pressure concentrates on the bone beneath the cartilage or when microscopic damage develops there. A swollen synovium may release inflammatory substances and pull the joint capsule taut, causing throbbing pain. When the knee is angled inward or outward, the load becomes concentrated on a particular joint surface. Weakened thigh muscles cannot adequately distribute the impact of walking. The subchondral bone, synovium, joint capsule, and surrounding muscles and ligaments each contribute to pain.(Jang Sunhee et al., 2021)
Age alone does not determine the rate of progression. A long-standing habit of working in a squatting position, bowed legs, previous meniscal or ligament injuries, thigh and hip strength, and the number of times a person climbs stairs each day all overlap. Among patients seen in clinical practice, it is not uncommon for only the knee injured in the past to deteriorate especially rapidly.
As body weight increases, so does the force the knees must withstand while walking. Substances secreted by adipose tissue are involved in the body's metabolic and inflammatory processes. This is why obesity affects osteoarthritis through both mechanical pressure on the knees and metabolic changes in the body.(Batushansky A et al., 2022) Weight management does more than reduce the load on the knees.
Symptoms and Imaging Must Be Considered Together to Explain Differences Between the Images and the Pain
It is not enough to ask only when the knee pain began. We ask specifically whether it hurts when taking the first step, whether it worsens after walking for a long time, and how many minutes morning stiffness lasts. We also check whether climbing or descending stairs is more difficult. If a stabbing pain occurs inside the joint when standing up after squatting, we first examine the cartilage and meniscus. Conversely, if the knee throbs at night even while resting in bed, we also check for synovial inflammation and other causes.
The first part of the physical examination assesses whether the knee can fully straighten and bend. If one thigh is noticeably thinner or the patient leans toward the opposite side when rising from a chair, muscle weakness and compensatory movement are likely to have developed. Weight-bearing X-rays are the standard examination for assessing joint-space width, osteophytes, and the condition of the bone beneath the cartilage.
Images and symptoms often do not match. When synovial inflammation is active or excessive stress is concentrated on the bone beneath the cartilage, severe pain may occur even without major changes on X-rays. Conversely, patients with extensive structural changes may still walk relatively long distances if they have little inflammation and preserved muscle strength. Clinicians diagnose knee osteoarthritis and determine the direction of treatment by considering the symptoms, physical examination, and imaging together.(Jang Sunhee et al., 2021)
Musculoskeletal ultrasound provides real-time images of joint fluid, the synovium, tendons, and bursae, which are difficult to assess with X-rays. During an injection, it can also be used to confirm the positions of the needle tip and the target structure. The use of ultrasound does not determine the treatment outcome. The intended treatment target must be clearly identified first.
MRI is not an examination that every patient needs from the outset. It is considered selectively when the symptoms are difficult to explain through a physical examination and X-rays alone or when the knee locks and cannot straighten. The same applies when a ligament or meniscal injury is suspected after trauma. The movements that trigger symptoms and the patient's actual functional limitations provide more important information than the number of examinations performed.
Nonsurgical Treatment Progresses from Weight Management and Exercise to Medications and Injections
When pain causes you to reduce your activity, your thigh muscles lose strength. This is why walking the same distance can place a greater perceived burden on your knees. Exercise and weight management are the first steps in nonsurgical treatment.(Brophy Robert H et al., 2022)
Exercise involves more than repeatedly bending and straightening the knee. You need to strengthen the quadriceps and gluteal muscles and restore movement in stiff joints. It also includes aerobic exercise within the joint’s tolerance, such as cycling or walking on level ground. Even if the pain increases slightly immediately after exercise, rather than stopping right away, check whether swelling and discomfort persist into the next day and adjust the frequency and intensity accordingly.
If sudden severe swelling, warmth, redness, or fever occurs, stop exercising and seek medical care. The same applies if you cannot bear weight after an injury or if the knee catches and cannot straighten. A systematic review evaluated exercise as a conservative treatment for pain and functional limitations in patients with knee osteoarthritis.(Raposo Filipe et al., 2021)
For patients who need to lose weight, we establish sustainable food intake and activity levels rather than pursuing major short-term changes. The goal is to reach a physical condition in which less pain accumulates while walking for the same amount of time and exercise can be maintained three times a week. The number on the scale is one indicator used to monitor that process.
If climbing stairs and walking remain difficult despite continued exercise and lifestyle adjustments, medication may be considered. Topical anti-inflammatory pain relievers are applied to the painful area. When selecting an oral anti-inflammatory pain reliever, the risk of gastrointestinal bleeding, kidney function, cardiovascular disease, and anticoagulant use should be assessed. Taking medication for a long time does not automatically mean moving to the next step. The function actually regained should be reassessed rather than focusing on the duration or dose of medication.
Intra-articular injections have different purposes and supporting evidence depending on the type. Steroids are selected for some patients with prominent synovial inflammation and swelling, with the aim of reducing pain in the short term.
Hyaluronic acid has been proposed to affect viscoelasticity and the inflammation-related environment inside the joint. Its clinical effectiveness and recommendation level vary among studies and clinical guidelines, and individual responses and the duration of benefit are also inconsistent. PRP is prepared by separating a platelet-rich component from the patient’s blood and injecting it into the joint. Growth factors released by the platelets participate in biological processes around joint tissues, improving the environment inside the joint and reducing pain.
Ozone injections may help when used together with prolotherapy or PRP treatment. Overall, these injections improve the binding and connections within the joint.
Extracorporeal shock wave therapy is not an injection that delivers medication into the joint cavity. It is a procedure that delivers acoustic energy to pain-generating soft tissues, such as the tendons and attachment sites around the knee.
Ultrasound or C-arm imaging is equipment used to confirm the target structure and needle position during procedures when needed.
In the treatment room, we compare not only pain on a 10-point scale but also the distance the patient can walk without resting and the number of stairs they can climb without using a handrail. We also check how often pain wakes the patient and how many days they exercised during the week. Even if the pain score remains similar, an increased walking distance and no nighttime awakenings provide grounds for continuing the current plan. If daily function continues to decline despite repeated treatments, we change direction, including considering a surgical evaluation, rather than repeating the same procedure.
When Daily Life and Sleep Remain Disrupted Despite Conservative Treatment, Surgery May Be Discussed
The timing of surgery is not determined by a single X-ray grade. The care team checks whether pain persists despite an appropriate period of exercise, weight management, medication, and any necessary injection therapy. Difficulty walking near home or using stairs and waking because of nighttime pain are also important considerations. The assessment also includes difficulty standing because the knee cannot fully straighten or leg deformity is progressing.
Joint replacement surgery removes damaged joint surfaces and replaces them with metal and polymer components. The decision is not made simply because the cartilage has worn down. When advanced arthritis causes substantial pain and functional impairment and nonsurgical treatment has not restored the targeted level of mobility, surgery may be discussed after an orthopedic evaluation.(Price Andrew J et al., 2018)
The duration of treatment is not applied mechanically either. Even after several months of conservative treatment, there may be room to redesign the treatment plan if only the medications were changed without evaluating muscle strength and walking ability. Conversely, if a person still has difficulty walking from the bedroom to the bathroom and sleeps poorly every night despite sufficiently adjusted treatment, continuing to delay a surgical evaluation may lead to further functional decline. When selecting and evaluating nonsurgical treatment before surgery, symptoms, mobility, risk factors, and previous responses should all be considered.(Brophy Robert H et al., 2022)
Age alone does not determine eligibility for surgery. Heart and lung function, diabetes control, and infection risk are assessed. The care team should also consider whether family members can assist with postoperative rehabilitation and whether the living environment is suitable. If the goal is to move around the home, treatment focuses on the ability to stand up without pain and walk short distances. If the patient wants to travel long distances or participate in recreational exercise, the evaluation also covers the strength needed to climb stairs, walking endurance, and joint range of motion. The final choice reflects the risks the patient is willing to accept and the patient’s preferences.
Long-term management continues after surgery. Thigh and hip strength should be maintained before surgery, and joint range of motion and walking ability should be restored gradually afterward. Body weight and activity level also affect the strain placed on the new joint. Patients who continue nonsurgical treatment should also have their walking distance, muscle strength, and progression of deformity reassessed at regular intervals.
When deciding whether to have surgery, the medical team considers more than imaging findings. They ask what activities the patient has given up because of pain and which treatments the patient has received and for how long. They also discuss how much treatment burden the patient is willing to accept to regain sleep and mobility. The goal is clear. It is not merely to suppress pain temporarily, but to restore recoverable function and maintain it over the long term.
This content is provided for medical information purposes and may vary depending on individual circumstances. Consultation with a specialist is recommended for an accurate diagnosis and appropriate treatment.
References
- Jang Sunhee, Lee Kijun, Ju Ji Hyeon (2021). Recent Updates of Diagnosis, Pathophysiology, and Treatment on Osteoarthritis of the Knee.. Int J Mol Sci. PMID: 33807695
- Batushansky A, Zhu S, Komaravolu R K (2022). Fundamentals of OA. An initiative of Osteoarthritis and Cartilage. Obesity and metabolic factors in OA.. Osteoarthritis Cartilage. PMID: 34537381
- Brophy Robert H, Fillingham Yale A (2022). AAOS Clinical Practice Guideline Summary: Management of Osteoarthritis of the Knee (Nonarthroplasty), Third Edition.. J Am Acad Orthop Surg. PMID: 35383651
- Raposo Filipe, Ramos Marta, Lúcia Cruz Ana (2021). Effects of exercise on knee osteoarthritis: A systematic review.. Musculoskeletal Care. PMID: 33666347
- Jawanda Harkirat, Khan Zeeshan A, Warrier Alec A (2024). Platelet-Rich Plasma, Bone Marrow Aspirate Concentrate, and Hyaluronic Acid Injections Outperform Corticosteroids in Pain and Function Scores at a Minimum of 6 Months as Intra-Articular Injections for Knee Osteoarthritis: A Systematic Review and Network Meta-analysis.. Arthroscopy. PMID: 38331363
- Price Andrew J, Alvand Abtin, Troelsen Anders (2018). Knee replacement.. Lancet. PMID: 30496082
Frequently Asked Questions
Q. If an X-ray shows significant cartilage loss, is surgery always necessary?
Even if imaging shows substantial changes, surgery is not necessarily recommended right away if pain is mild and daily function is preserved. The location and severity of pain, joint range of motion, walking ability, and response to nonsurgical treatment are evaluated together.
Q. Can I continue walking and strength training if I have knee osteoarthritis?
You can continue walking and strength training within your joints’ tolerance. If pain or swelling after exercise remains noticeable into the next day, you should reduce the distance, number of repetitions, or intensity accordingly.
Q. How does the appropriate timing for knee injections vary by type?
Depending on their ingredients, injections may differ in how they reduce inflammation and pain, how quickly they take effect, and how long their effects last. The decision on whether and when to administer an injection is based on joint swelling and warmth, the nature of the pain, coexisting conditions, and the response to previous injections.
Q. How long should I receive nonsurgical treatment before considering joint replacement surgery?
Joint replacement surgery is not recommended simply because you have completed a set treatment period. What matters is whether essential functions such as walking, climbing stairs, and sleeping remain limited despite appropriate adjustments to treatments such as exercise, medication, and injections.
Q. Why is the pain severe even though the X-ray changes are not significant?
Because X-rays mainly show bones and joint spaces, they may not adequately reveal synovial inflammation, joint capsule irritation, or problems with the meniscus or tendons. The need for additional tests, such as ultrasound or MRI, is determined based on the location of the pain and physical examination findings.