Knee Pain
Symptoms, Causes & Treatment
Understanding knee pain: what causes it, how it is investigated, and the most effective treatments from physiotherapy to surgery.
What Is Knee Pain?
Knee pain is one of the most common musculoskeletal complaints affecting people of all ages. In younger patients, sports injuries — ACL tears, meniscal tears, and patellofemoral pain syndrome — predominate. In older patients, osteoarthritis is the most common cause.
The knee is a complex joint with multiple structures that can be injured or degenerate. Accurate assessment of which structure is causing pain determines the appropriate treatment.
What Are the Symptoms of Knee Pain?
The location, onset, and associated features of knee pain are the key diagnostic features.
Knee pain localised to front, side, or back of knee · Swelling or effusion (fluid in knee) · Locking or giving way of knee · Reduced ability to fully extend or flex · Crepitus on movement · Tenderness on palpation of joint line
Sudden knee locking after twisting (possible meniscal tear) · Haemarthrosis (rapid swelling after injury — possible ACL rupture or fracture) · Knee giving way repeatedly · Hot, red, swollen knee with fever (septic arthritis)
Rapid, significant knee swelling immediately after a twisting injury suggests haemarthrosis (blood in the joint) from an ACL tear or fracture. Attend A&E or orthopaedic urgent care the same day.
What Causes Knee Pain?
Knee pain has numerous causes depending on age, mechanism of injury, and location of pain. Accurate anatomical localisation and history of injury or gradual onset guide the diagnosis.
Patellofemoral pain syndrome (runner's knee) is the most common cause of anterior knee pain. It results from maltracking of the patella, causing pain on stairs, squatting, and prolonged sitting.
Meniscal tears occur from twisting injuries and cause joint line tenderness, locking, and giving way. The ACL is commonly torn with pivoting injuries, producing haemarthrosis and instability. Both may require surgical management.
Osteoarthritis (OA) causes progressive loss of articular cartilage, subchondral bone remodelling, and osteophyte formation. It is the most common cause of chronic joint pain in adults over 50, affecting knees, hips, hands, and spine.
Rheumatoid arthritis (RA) is a systemic autoimmune disease in which the immune system attacks synovial joints, causing chronic synovitis, joint erosion, deformity, and systemic inflammation. Anti-CCP antibodies are highly specific.
Non-specific low back pain (no identifiable cause) accounts for 85% of presentations. Disc herniation, facet joint degeneration, and muscle/ligament strain are the most common structural causes. Poor posture and sedentary lifestyle are key contributors.
Muscle strains occur when muscle fibres are overstretched or torn. Grade 1 = mild stretch; Grade 2 = partial tear; Grade 3 = complete rupture. Eccentric muscle loading during sprinting, jumping, or lifting is the most common mechanism.
Key Risk Factors
How Is Knee Pain Diagnosed?
Clinical assessment including Lachman test (ACL), McMurray test (meniscus), and effusion assessment guides investigation. Imaging is required for significant injury or when surgery is being considered.
How Is Knee Pain Treated?
Treatment ranges from conservative physiotherapy for most presentations to surgical reconstruction for complete ligament ruptures and knee replacement for severe OA.
Supportive Measures
RICE for acute injuries, NSAIDs for inflammation, quadriceps and hip strengthening exercises for patellofemoral pain, and weight management for OA are the most effective self-management strategies.
When Knee Pain Needs Specialist Review
Recurrent knee pain not controlled with physiotherapy and analgesia warrants specialist orthopaedic review. For OA, knee replacement is highly effective at restoring function and quality of life. For ligament injuries with persistent instability, surgical reconstruction may be appropriate.
When Should You Seek Medical Advice for Knee Pain?
Sudden knee haemarthrosis (rapid significant swelling after injury) — possible ACL rupture or fracture · Hot, swollen knee with fever (septic arthritis) · Complete knee locking unable to extend · Inability to weight bear after trauma.
Sudden significant knee swelling after injury · Knee locking and inability to fully extend · Hot, swollen knee with fever · Knee giving way repeatedly · OA pain not controlled with analgesia and physiotherapy.
How to Protect Your Knees
Knee pain prevention focuses on maintaining strong muscles around the joint, healthy weight, and appropriate training load.
Warm up adequately before exercise and cool down after. Increase training load gradually (the 10% rule). Strengthen muscles around vulnerable joints (glutes for knee, rotator cuff for shoulder, core for back) to reduce injury risk.
Weight management reduces load on weight-bearing joints. Every 1kg of body weight loss reduces knee joint loading by 4kg. Low-impact exercise (swimming, cycling) maintains fitness without joint stress.
Physiotherapy-led exercise is more effective than rest for most MSK conditions. Strengthening exercises for the muscles around affected joints reduce pain and improve function. Ask for a referral or self-refer where available.
Proprioception (balance) retraining after ankle sprain significantly reduces recurrence risk. Simple exercises: single-leg standing, wobble board training — start while holding support and progress to unsupported over 4–6 weeks.
Maintain strong, flexible muscles around the spine and joints. Core strengthening (Pilates, swimming), hip strengthening (glute exercises), and hamstring stretching are the most evidence-based approaches for back pain and sciatica prevention.
Supportive footwear with good arch support and cushioning is the most important non-pharmacological treatment for plantar fasciitis. Avoid walking barefoot on hard floors, especially in the morning. Replace sports shoes every 500 miles.
Speak to a Clinician About Knee Pain
Through The GP Service, a licensed clinician can assess your knee pain, arrange investigations, recommend physiotherapy, and refer to orthopaedics where appropriate.



Expert clinical advice, when you need it.
Knee Pain FAQs
Most rotator cuff problems — tendinopathy, partial tears, and impingement — respond well to physiotherapy. A targeted physiotherapy programme addressing rotator cuff strength and scapular control resolves 70–80% of cases within 3–6 months. Steroid injection provides short-term relief but does not improve long-term outcomes. Full-thickness rotator cuff tears with significant weakness warrant MRI assessment and possible surgical repair, especially in younger or active patients. Frozen shoulder runs a natural history of 1–3 years and usually resolves fully without surgery.
Joint pain with a hot, red, severely swollen joint and fever is a red flag for septic arthritis — a surgical emergency. This requires same-day joint aspiration and IV antibiotics. Joint pain without these features requires investigation to determine the cause: OA, RA, gout, or reactive arthritis. Getting the right diagnosis quickly matters because RA causes joint erosion within weeks to months of onset, and early DMARD treatment dramatically reduces long-term disability.
OA affects cartilage and causes pain that worsens with use and eases with rest. RA is an autoimmune disease causing symmetrical synovial inflammation, morning stiffness >1 hour, systemic symptoms, and elevated inflammatory markers. RA gets worse without treatment and causes irreversible joint destruction; OA does not have systemic consequences. Getting the right diagnosis early is important because the treatments are completely different. If you have morning stiffness lasting over an hour and symmetrical joint swelling, see a clinician urgently for RA screening.
Most back pain is non-specific — caused by muscle, ligament, or disc strain without any serious underlying cause. The vast majority resolves within 4–6 weeks. Key red flags to watch for: bladder or bowel changes (possible cauda equina syndrome — call 999), fever, unexplained weight loss, or pain that is unrelenting at night regardless of position. If none of these are present, staying active, taking regular analgesia, and seeing a physiotherapist is the most effective approach.
Bed rest is not recommended and actually slows recovery. Staying as active as pain allows — walking, gentle stretching, swimming — helps the back heal faster. Most non-specific back pain improves within 4–6 weeks with movement, NSAIDs, and physiotherapy. Seeing a physiotherapist early produces better outcomes than waiting. If back pain has not improved after 6 weeks, or is worsening, a GP review is warranted to consider imaging and further management.
Sciatica is caused by compression of the sciatic nerve or its nerve roots — most commonly from a disc herniation at L4/5 or L5/S1. Around 80–90% of sciatica resolves within 6–12 weeks with conservative management: staying active, NSAIDs, physiotherapy, and nerve pain medication if needed. Red flags requiring emergency assessment: loss of bladder or bowel control, saddle numbness, or rapidly progressive leg weakness. These could indicate cauda equina syndrome, which is a surgical emergency.
Allopurinol should never be started during an acute gout attack as this can prolong or worsen the flare. It should be started 2–4 weeks after the acute attack has settled, ideally while continuing prophylactic colchicine or NSAID cover for the first 3–6 months. Start at 100mg daily and increase every 4 weeks to achieve a target serum urate below 360 μmol/L. Once on a stable dose, allopurinol is continued indefinitely. Stopping and restarting is a common cause of recurrent attacks.
Most ankle sprains heal within 6–8 weeks. Grade 1 (stretching) and Grade 2 (partial tear) injuries resolve with physiotherapy and graded return to sport. Grade 3 (complete ligament rupture) may require immobilisation or, rarely, surgery. Proprioception training is essential to prevent recurrence — recurrent ankle sprains dramatically increase long-term instability and OA risk. If you cannot weight bear after an ankle injury, apply the Ottawa rules: inability to weight bear plus bony tenderness at the malleolus warrants an X-ray to exclude fracture.
