What's Wrong With My Knee?

⚠ Clinical Note

This article is for educational purposes only. It is based on current clinical practice guidelines and peer-reviewed research and is not a substitute for personalised medical advice, diagnosis, or treatment. If you have knee pain or any concerns about your symptoms, consult a qualified healthcare professional before starting any exercise or treatment program.

Key Facts

✔ Over 2.1 million Australians were estimated to have osteoarthritis in 2022, and knee OA is a leading driver of disability for people over 50. [1]
✔ Knee osteoarthritis can be confidently diagnosed based on clinical assessment alone - imaging is not routinely needed and adds little to initial management decisions. [1,2]
✔ Exercise is the most strongly recommended first-line treatment for knee osteoarthritis, regardless of age, pain level, or how much structural change has occurred - and there is strong evidence that supervised exercise programs reduce pain and improve function. [2,5,6,11]
✔ For most degenerative meniscal tears, structured physiotherapy produces outcomes equivalent to arthroscopic partial meniscectomy (APM). [10]
✔ Patellofemoral pain - aching around the kneecap - is one of the most common knee presentations and responds well to combined hip and knee exercise therapy. [3]
✔ ACL injuries carry a second-injury rate of around 15% overall, rising to 21% in people under 25 - making proper rehabilitation and prevention programs important after any significant ligament injury. [4]

30-Second Summary

Knee pain has several common causes - osteoarthritis, patellofemoral pain, meniscal tears, and ligament injuries being the most frequent - and the right treatment depends on which structure is involved and why. For most presentations, exercise-based rehabilitation is the most effective first approach, and surgery is rarely needed as a first step. If your knee has been bothering you for more than a few weeks, or if it swelled suddenly or gave way, a clinical assessment is the right starting point.

Introduction

The knee is the largest and one of the most complex joints in the body. It handles everything from climbing stairs to running on uneven ground, relying on cartilage, ligaments, tendons, and muscle to do so. That complexity also means there are several different structures that can cause pain when something goes wrong.
What's wrong with my knee? is a question that often goes unanswered for longer than it should. Some people assume they need a scan before anything can be done. Others assume it's just age, or that surgery is eventually inevitable. Neither is usually true. Most knee pain has a definable cause, a clear evidence-based treatment path, and a good prognosis when managed appropriately.

What's Actually Going On in a Painful Knee?

The knee joint brings together the femur (thigh bone), tibia (shin bone), and patella (kneecap). Between the femur and tibia sit two C-shaped wedges of cartilage called the menisci - they act as shock absorbers and help distribute load across the joint. The joint itself is lined with articular cartilage, which allows smooth movement.
Four major ligaments - the ACL, PCL, MCL, and LCL - control stability and movement. Around the joint, tendons and bursae (small fluid-filled sacs) allow muscles to pull on bone without friction.
Pain can arise from any one of these structures. The location of your pain, how it came on, what makes it better or worse, and your age and activity level all point toward which structure is most likely involved. That's why a good clinical history and physical examination can narrow down the diagnosis accurately - often without the need for imaging. [1,2]

Common Causes of Knee Pain

Osteoarthritis

Knee osteoarthritis (OA) is the most common form of knee pain in adults over 45. It occurs when the cartilage lining the joint gradually wears down, leading to pain, stiffness, and sometimes swelling. In 2022, over 2.1 million Australians were estimated to have OA, and its prevalence rises sharply from the mid-40s onward. [1]
A few things are worth knowing right away. OA is not an inevitable consequence of ageing - it's a clinical condition with real risk factors, and those factors are largely modifiable. [1] Being overweight doubles the risk of developing knee OA; obesity increases it fourfold. [1]
Structural changes on a scan don't always correlate with pain - some people have significant cartilage change and little discomfort, while others have minimal imaging change and significant symptoms. [1,2] This is why treatment decisions are guided by what you're experiencing, not what a scan shows.
The cardinal symptoms are morning stiffness easing within 30 minutes, pain that worsens with activity, and gradual onset rather than sudden injury. [1,2] People with knee OA often notice difficulty with walking, stair climbing, rising from a chair, and getting in and out of cars. [1]

Patellofemoral Pain

Patellofemoral pain (PFP) is pain around or behind the kneecap, and it is one of the most common knee presentations across all ages. The onset is usually gradual and without a specific injury. Symptoms worsen when the knee is loaded in a bent position - squatting, stair climbing, prolonged sitting, or running, especially on hills. [3]
PFP can stem from overuse, muscle imbalance around the hip and quadriceps, movement patterns that place extra load on the kneecap, or a combination of factors. It often presents as a vague, poorly-defined aching at the front of the knee. [3] Patients sometimes describe the pain as behind the kneecap or "around the whole kneecap area." Young, active adults are frequently affected, though PFP is not limited to this group.

Meniscal Tears

The menisci can tear in two very different ways, and the type matters for treatment. Acute tears typically happen during a twisting injury - a soccer player pivoting with the foot planted, for example. They may cause sudden pain, swelling, and sometimes a sensation of the knee locking or giving way. Degenerative tears, on the other hand, develop gradually in older adults and are often found on MRI without the person having had any specific injury. [8,9]
Meniscal tears are actually the most common knee pathology, with a mean annual incidence of 66 per 100,000 people. [8] MRI studies of asymptomatic adults show that about 10% of healthy, uninjured knees already have meniscal changes on imaging - rising to around 19% in people over 40. [7] This is why a meniscal tear found on scan isn't always the explanation for someone's knee pain. Degenerative changes in the meniscus are a normal feature of an ageing joint.

Ligament Injuries

The knee's four ligaments control its stability during movement. The ACL (anterior cruciate ligament) and MCL (medial collateral ligament) are the most commonly injured. ACL injuries typically occur during non-contact deceleration or cutting movements - approximately 70% of ACL injuries involve no direct contact with another player. [4] MCL injuries often result from a direct blow to the outer knee, pushing it inward.
Ligament injuries are graded from mild sprains (Grade I - fibres stretched but intact) to complete ruptures (Grade III - full tear). A complete ACL rupture in an active person usually requires a structured decision between rehabilitation alone and surgical reconstruction, based on instability, activity demands, and the individual's goals. [4] Most MCL injuries, including significant ones, respond well to physiotherapy-guided rehabilitation and do not require surgery. [4,12]

Other Common Causes

Other structures that can cause knee pain include the patellar tendon (patellar tendinopathy), the IT band (iliotibial band syndrome), and bursae around the knee (bursitis). These each have distinct presentations and management approaches. Tendinopathy assessment and load management follow principles similar to those described in the Achilles tendon pain guide, which applies equally to patellar tendon presentations. Pain felt at the knee also occasionally originates from the lower back or hip - lower back pain causes and management explains how lumbar spine conditions are assessed and distinguished from true knee pathology.

Symptoms: What to Pay Attention To

Different causes of knee pain tend to present differently. A few patterns worth noting:
Osteoarthritis typically involves gradual-onset pain that has developed over months or years, morning stiffness that loosens up within about 30 minutes, and pain that's worse after activity. [1,2]
Patellofemoral pain is most noticeable during knee-bending activities - stairs, squatting, or sitting for long periods. The pain is usually at the front or around the kneecap. [3]
Meniscal tears may cause joint-line tenderness (pain along the sides of the knee), swelling within a few hours of injury, and sometimes a sensation of clicking or catching. [8,12] True locking - where the knee genuinely cannot straighten - is less common but important to report promptly. [8,12]
Ligament injuries typically involve a sudden-onset event, often with an audible pop and significant swelling within the first few hours. [4,12] The knee may feel unstable during weight bearing, and pain tends to be localised to the injured ligament's area. [4,12]
Seek urgent assessment if your knee swells rapidly after an injury, if you cannot put weight on it, or if it appears visibly deformed. [12] Fever combined with knee pain and swelling may indicate a joint infection and requires prompt medical attention. [12]

Treatment Options

The right treatment depends entirely on the cause - but several principles apply across most knee conditions.

Exercise and Physiotherapy

For knee osteoarthritis, exercise is the single most strongly recommended treatment in every major Australian and international guideline. [1,2,5,6] The Australian Physiotherapy Association confirms that supervised exercise programs focusing on lower limb strengthening, flexibility, and balance reduce pain and improve function in knee OA. [11] Land-based exercise - walking, muscle-strengthening programs, and Tai Chi - is strongly recommended for all people with knee OA, regardless of age, severity of structural change, or current pain levels. [2] Exercise reduces pain, improves function, and supports weight management. [1,2]
For patellofemoral pain, combined hip- and knee-targeted exercise therapy is strongly recommended as first-line treatment - the highest level of clinical evidence (Grade A) supports this approach. [3] Targeting the posterolateral hip muscles alongside quadriceps work produces better outcomes than knee-targeted exercise alone. [3]
For ligament injuries, supervised rehabilitation with progressive weight-bearing and neuromuscular re-education - retraining the muscles and nervous system to control joint movement accurately - is the foundation of recovery. [4] After ACL reconstruction, evidence strongly supports a structured strengthening program running two to three times per week over six to ten months. [4] Strength and conditioning rehabilitation at RheCore follows this progressive loading approach for both ligament and OA presentations.

Medicines

For knee OA, NSAIDs (non-steroidal anti-inflammatory drugs such as ibuprofen) are the preferred first-line medication when medication is needed, used at the lowest effective dose for the shortest time possible. [1] Topical NSAIDs are a useful option with fewer systemic side effects. [1]
Opioids are not recommended for knee OA - the risk of harm outweighs any benefit for most people. [1] Glucosamine, chondroitin, fish oil, and PRP injections are also not supported by current guidelines. [1,2,5,6]

When Surgery Is and Isn't Indicated

Surgery is important for some patients - but it is rarely the right first step for most knee conditions.
For knee OA, arthroscopic procedures (including lavage, debridement, and partial meniscectomy) are not recommended. [1,2,6] They provide no clinically meaningful benefit over non-surgical management, and current Australian guidelines strongly recommend against them. [1,2] Between 2015 and 2022, Medicare Benefits Schedule (MBS) claims for knee arthroscopy in people aged 45 and over fell by 47% in Australia as the evidence caught up with practice. [1]
For degenerative meniscal tears specifically - the kind that develops gradually rather than from a specific injury - the evidence is now consistent across multiple randomised trials. The FIDELITY trial was a multicentre, double-blind, sham-controlled randomised controlled trial (RCT) involving 146 adults with degenerative medial meniscal tears and no knee OA. APM produced no significant improvement in pain, function, or quality of life compared with placebo surgery at 12 months. [9]
This finding held at 24 months [10] and at 5 years, where APM was associated with a slightly increased risk of radiographic OA progression alongside no additional benefit in patient-reported outcomes. [13] Several systematic reviews of pooled RCT data confirm the same conclusion. [7] Structured physiotherapy achieves comparable outcomes and clinicians should offer it as first-line treatment. [8]
Meniscal repair stitches a torn meniscus back together rather than removing tissue. It is appropriate for acute, traumatic tears within the vascular zone of the meniscus - most often in younger patients. Preserving meniscal tissue reduces the longer-term risk of OA compared with meniscectomy. [8] This is a meaningful clinical distinction: what kind of tear is it, and whose knee is it in?
For ACL ruptures, reconstruction may be appropriate depending on instability, activity demands, and the person's goals. [4,12] Many people with ACL injuries manage well with non-operative rehabilitation alone - particularly older adults or those with lower activity demands. [4,12] This decision is best made with a clinician who knows your situation. Post-surgical rehabilitation at RheCore covers the structured recovery pathway for people who proceed with knee surgery.
Joint replacement surgery (knee arthroplasty) remains appropriate for people with severe, disabling OA that has not responded to optimal non-surgical management. Most people who are physically active and maintain a healthy weight can delay or avoid this outcome. [1]

Self-Management

For new soft-tissue injuries, use the PEACE & LOVE framework. In the first few days: Protection (avoid painful activities), Elevation, Avoid anti-inflammatories and ice, Compression, and Education. [12] After that initial phase: Load (guided return to activity), Optimism, Vascularisation (pain-free movement), and Exercise (active recovery). [12] Applying ice and anti-inflammatories immediately after injury is no longer recommended, as this can interfere with the body's natural healing response. [12]
Stay active. Exercise programs that increase physical activity and muscle strength reduce associated pain and disability in knee OA. [1] Avoiding activity tends to worsen pain over time, weaken supporting muscles, and increase functional decline. [1,2] The goal is not rest - it is load management. Finding the right level and type of activity for your current presentation is what a physiotherapist can help you calibrate.
Address weight if relevant. If you carry excess weight, even modest reduction can meaningfully reduce knee OA symptoms and slow progression. [1,2] People who are overweight have double the risk of developing knee OA; obesity increases this to fourfold. [1] Weight management is therefore one of the most evidence-supported long-term strategies available. [1] The strongest approach combines dietary changes with regular exercise. [5]
Build quad and hip strength. Weakness in the quadriceps (front of the thigh) and hip abductors (outer hip muscles) consistently correlates with both OA-related pain and disability and patellofemoral pain. [1,3] Strengthening these muscle groups - even with basic home exercises - reduces pain and improves function. [1,3]
Manage flares without fear. OA symptoms fluctuate - a bad few days does not mean things are getting worse. Keeping moving through a manageable flare, rather than stopping activity entirely, supports better long-term outcomes. [1] For people managing persistent or recurrent knee pain, RheCore's chronic pain management program takes a structured, evidence-based approach to long-term self-management.

When to See a Physiotherapist

You don't need to be in severe pain to see a physiotherapist, and you don't need a referral from a GP. A physiotherapist can assess which structure is driving your symptoms and whether your pain is genuinely from the knee or referred from the lower back or hip. These presentations are worth having assessed:

• Pain that has persisted for more than two to three weeks without a clear explanation or improvement
• Knee pain that's stopping you from doing activities you normally do - walking, sport, work tasks
• Gradual-onset front-knee pain aggravated by stairs, squatting, or sitting for extended periods
• A knee that swells regularly or feels unstable during direction changes
• Morning stiffness that you're managing with activity modifications

Seek urgent medical assessment for the following:

• Sudden, severe swelling after an injury
• particularly within the first few hours
• Inability to put weight on the leg
• A knee that feels genuinely locked and cannot straighten
• Fever, redness, and warmth around the joint
• Numbness, tingling, or weakness extending down the leg

These signs may indicate more serious pathology requiring same-day or emergency medical review, rather than a physiotherapy appointment.

Key Takeaways

• Knee pain has several common causes - OA, patellofemoral pain, meniscal tears, and ligament injuries - each with a distinct presentation and treatment path.
• Exercise is the most robustly evidenced treatment for knee OA and patellofemoral pain, and should not be avoided because the knee is painful.
• Imaging is not required to start treatment, and scan findings - particularly degenerative meniscal changes - do not always explain a person's pain.
• Arthroscopic surgery is not recommended for knee OA or degenerative meniscal tears; evidence shows it offers no advantage over non-surgical care for these presentations.
• Acute ligament and traumatic meniscal injuries need early assessment to determine the right rehabilitation approach, which may or may not include surgery.

References

1. Australian Commission on Safety and Quality in Health Care. *Osteoarthritis of the Knee Clinical Care Standard*. Sydney: ACSQHC; 2024.
2. The Royal Australian College of General Practitioners. *Guideline for the Management of Knee and Hip Osteoarthritis*. 2nd edition. East Melbourne: RACGP; 2018.
3. Willy RW, Hoglund LT, Barton CJ, et al. Patellofemoral Pain: Clinical Practice Guidelines Linked to the International Classification of Functioning, Disability and Health. *J Orthop Sports Phys Ther.* 2019;49(9):CPG1-CPG95. doi:10.2519/jospt.2019.0302
4. Logerstedt DS, Scalzitti DA, Bennell KL, et al. Knee Stability and Movement Coordination Impairments: Knee Ligament Sprain Revision 2017. *J Orthop Sports Phys Ther.* 2017;47(11):A1-A47. doi:10.2519/jospt.2017.0303
5. Gibbs AJ, Gray B, Wallis JA, et al. Recommendations for the Management of Hip and Knee Osteoarthritis: A Systematic Review of Clinical Practice Guidelines. *Osteoarthritis and Cartilage.* 2023;31:1280–1292. doi:10.1016/j.joca.2023.05.015
6. Conley B, Bunzli S, Bullen J, et al. Core Recommendations for Osteoarthritis Care: A Systematic Review of Clinical Practice Guidelines. *Arthritis Care & Research.* 2023;75(9):1897–1907. doi:10.1002/acr.25101
7. Smoak JB, Matthews JR, Vinod AV, Kluczynski MA, Bisson LJ. An Up-to-Date Review of the Meniscus Literature: A Systematic Summary of Systematic Reviews and Meta-Analyses. *Orthopaedic Journal of Sports Medicine.* 2020;8(9):2325967120950306. doi:10.1177/2325967120950306
8. Mordecai SC, Al-Hadithy N, Ware HE, Gupte CM. Treatment of Meniscal Tears: An Evidence Based Approach. *World Journal of Orthopaedics.* 2014;5(3):233–241. doi:10.5312/wjo.v5.i3.233
9. Sihvonen R, Paavola M, Malmivaara A, et al. (FIDELITY Group). Arthroscopic Partial Meniscectomy versus Sham Surgery for a Degenerative Meniscal Tear. *N Engl J Med.* 2013;369(26):2515–2524. doi:10.1056/NEJMoa1305189
10. Sihvonen R, Paavola M, Malmivaara A, et al. (FIDELITY Group). Arthroscopic Partial Meniscectomy versus Placebo Surgery for a Degenerative Meniscus Tear: a 2-Year Follow-Up of the Randomised Controlled Trial. *Ann Rheum Dis.* 2018;77:188–195. doi:10.1136/annrheumdis-2017-211172
11. Bennell K, Hinman R, Crossley K. APA Position Statement: Physiotherapy Management of Knee Joint Osteoarthritis. Australian Physiotherapy Association; produced by Sports Physiotherapy Australia and Musculoskeletal Physiotherapy Australia.
12. Healthdirect Australia. Knee Injuries - Symptoms, Treatments and Causes. Reviewed December 2023.
13. Sihvonen R, Paavola M, Malmivaara A, et al. (FIDELITY Group). Arthroscopic Partial Meniscectomy for a Degenerative Meniscus Tear: a 5-Year Follow-Up of the Placebo-Surgery Controlled FIDELITY Trial. *Br J Sports Med.* 2020;54(22):1332–1339. doi:10.1136/bjsports-2020-102813