Knee Pain– Causes, Symptoms, Diagnosis, Treatment and Ongoing care
Knee pain is a common complaint in the outpatient setting. Onset may be acute or chronic, or it may present as an acute exacerbation of a chronic condition. Trauma, overuse, and degenerative conditions are frequent causes. Acuity of onset, patient age, pain location, associated symptoms, and mechanism of injury can help to narrow the extensive differential diagnosis.
- Knee pain accounts for 1.9 million primary care visits annually (1).
- 42% of runners experience a knee injury each year (2).
- The knee is the most common site of lower extremity injury among runners (3).
- Patellofemoral pain syndrome is the most common diagnosis in runners (2).
- Osteoarthritis (OA) accounts for 34% of adult acute-onset knee pain in the primary care setting (1): One of the leading causes of disability in the US.
- Rapid increases in training volume and intensity
- Extremity malalignment
- Poor flexibility, muscle imbalance/weakness
- Previous injuries
- Activities involving cutting, jumping, deceleration
- Maintain normal body mass index (BMI): Weight loss if obese.
- Use sound exercise training principles.
- Correct strength and flexibility imbalances.
- Trauma (ligament injury, meniscal injury, fracture)
- Overuse (tendinopathy, apophysitis)
- Rheumatologic conditions; arthritis
- Infectious (bacterial, postviral)
Commonly Associated Conditions
- Avulsion, stress, or other fractures
- Patellar dislocation/subluxation
- Meniscal injury
- Ligamentous injury
- Septic joint
- Osteochondral injury
May recall mechanism: Deceleration, hyperextension, and cutting are common mechanisms for anterior cruciate ligament (ACL) tear.
- Popping, giving way, and rapid marked effusion are common in ACL injury and patellar subluxation.
- Hyperflexion, fall on flexed knee, and “dashboard injury” are seen in posterior cruciate ligament (PCL) injury.
- Hemarthrosis is common in patellar subluxation, ACL injury.
- Twisting on planted foot is a common mechanism for meniscal injury.
- Stiffness/pain with prolonged sitting
- Pain ascending/descending stairs often implies meniscal injury.
- Lateral/inferior knee pain often is seen in iliotibial band syndrome.
- Medial/inferior knee pain is seen in anserine bursitis.
- Swelling and/or effusion
- Decreased range of motion (ROM)
- Joint instability
- Locking or catching
- Observe for antalgic gait, dynamic patellar tracking abnormalities.
- Inspect for malalignment, muscle atrophy.
- Palpate for effusion, swelling, erythema, warmth, and tenderness.
- Evaluate for strength imbalances.
- Evaluate ROM and flexibility.
Diagnostic Tests & Interpretation
- Lachman test assesses ACL integrity.
- Posterior drawer assesses PCL integrity.
- Posterior sag sign reflects PCL integrity.
- Apprehension test assesses patellar dislocation.
- Patellar grind test assesses patellar dysfunction.
- Valgus/varus stress test assesses medial/lateral collateral ligament (MCL/LCL) integrity.
- McMurray test assesses meniscal tears.
- Ober test assesses iliotibial band (ITB) tightness.
- Septic joint, gout, pseudogout:
- Arthrocentesis with synovial fluid analysis, cell count, Gram stain, culture
- If rheumatoid arthritis suspected:
- Complete blood count, erythrocyte sedimentation rate, rheumatoid arthritis
- Atraumatic joint edema (and possibly migratory): Consider Lyme disease titer.
- Radiographs may be needed to rule out fracture in patients with acute knee trauma.
- Knee films (Ottawa knee rules) (1)[A]:
- Age >55 years or
- Tenderness at the patella or fibular head or
- Inability to bear weight 4 steps or
- Inability to flex knee to 90°
- Radiographs for suspicion of avulsion, stress fracture, or patellofemoral pathology
- Upright anteroposterior (AP), lateral, Merchant, and tunnel views may be helpful in the diagnosis of OA.
- MRI is “gold standard” for imaging muscle, ligamentous, and intraarticular structures; used when surgery is next step in treatment.
- CT scan may be required if occult fracture is suspected.
Arthroscopy may be beneficial in the diagnosis of certain conditions.
- Acute onset:
- Contusion; fracture; meniscal, cruciate, or collateral ligament tear; extensor tendon injury
- OA, osteomyelitis, septic arthritis, gout, or pseudogout
- Insidious onset: Patellofemoral pain syndrome, iliotibial band syndrome, OA, rheumatoid arthritis (RA), bursitis, tumors, tendinopathy, loose bodies, bipartite patella, degenerative meniscal tears
- Anterior pain: Patellar/quadriceps tendinopathy, patellofemoral pain syndrome, patellar injury, OA, bursitis, fat pad impingement
- Posterior pain: Popliteal cyst, popliteal aneurysm, medial meniscus tear, tumors
- Medial pain: OA, meniscal or MCL injury, pes anserine bursitis, plica
- Lateral pain: Iliotibial band syndrome, lateral meniscus or LCL injury, OA
OA, degenerative meniscal tears, and gout are more common.
- 3 million pediatric sports injuries occur annually.
- Must be concerned about physeal/apophyseal and joint surface injuries in the skeletally immature:
- Acute injuries: Patellar subluxation, avulsion fractures, ACL tear
- Overuse injuries: Patellar femoral syndrome, apophysitis, osteochondritis desiccans, patellar tendonitis, stress fracture (4)[C]
- Neoplasm; juvenile RA
- Referred pain from slipped capital femoral epiphysis
- Nonsteroidal anti-inflammatory drugs (NSAIDs):
- Acute ligament sprains, muscle strains, tendinopathy (5)[C]:
- Ibuprofen: 200–800 mg t.i.d.
- Naproxen: 375–500 mg b.i.d.
- Indomethacin: 25–50 mg t.i.d.
- Not recommended in fracture, stress fracture, chronic muscle injury; may be associated with delayed healing; low dose and brief course only if necessary (5)[C]
- Effective in short-term pain reduction in OA, but long-term use is not recommended owing to risks of significant adverse effects (6)[A].
- Acute ligament sprains, muscle strains, tendinopathy (5)[C]:
- Acetaminophen: Doses up to 4 g/d are safe and effective in OA (7)[A].
- Intraarticular corticosteroid injection may provide short-term benefit in knee OA (8)[A].
Acute injury: PRICEMM therapy (protection, relative rest, ice, compression, elevation, medications, modalities)
Issues for Referral
- Joint instability
- Lack of improvement with conservative measures
- Salter-Harris physeal fractures
- Physical therapy is recommended as initial treatment for patellofemoral pain syndrome (9)[A].
- Therapeutic exercise improves function and reduces pain in OA (10)[A].
Complementary and Alternative Medicine
Glucosamine sulfate, 1,500 mg/d, may provide moderate pain reduction and improved function in OA (11)[B].
- Surgery may be required for ligamentous and cartilaginous injuries.
- Chronic conditions refractory to conservative therapy may require surgical intervention.
- Activity modification in overuse conditions
- Rehabilitative exercise in OA:
- Low-impact exercise: Walking, swimming, cycling
- Strength, ROM, and proprioceptive training
- After initial treatment in acute injury, consider rehabilitation.
- In chronic and overuse conditions, assess functional status, rehabilitative exercise compliance, and pain control at follow-up visit.
Weight reduction for overweight patient with OA
- Review activity modifications.
- Encourage the patient to play an active role in the rehabilitative process.
- Review risks and benefits of pharmaceutical interventions.
Varies with diagnosis, severity of injury, chronicity of condition, patient motivation to participate in rehabilitative exercises, and whether surgical intervention is required
- Chronic joint instability
1. Jackson JL, O’Malley PG, Kroenke K. Evaluation of acute knee pain in primary care. Ann Intern Med. 2003;129:575–88.
2. Taunton JE, Ryan MB, Clement DB, et al. A retrospective case-control analysis of 2002 running injuries. Br J Sports Med. 2002;36:95–101.
3. van Gent RN et al. Incidence and determinents of lower extremity running injuries in long distance runners: a systematic review. Br J Sports Med. 2007;41:469–80.
4. Caine D, DiFiori J, Maffulli N. Physeal injuries in children’s and youth sports: reasons for concern? Br J Sports Med. 2006;40:749–60.
5. Mehallo CJ, Drezner JA, Bytomski JR. Practical management: Nonsteroidal anti-inflammatory drug use in athletic injuries. Clin J Sports Med. 2006;16:170–74.
6. Bjordal JM, Ljunggren AE, Klovning A, et al. Non-steroidal anti-inflammatory drugs, including cyclo-oxygenase-2 inhibitors, in osteoarthritic knee pain: Meta-analysis of randomized placebo controlled trials.Brit J Med. 2004;329:1317.
7. Zhang W, Jones A, Doherty M. Does paracetamol (acetaminophen) reduce the pain of osteoarthritis? A meta-analysis of randomized controlled trials. Annals Rheum Dis. 2004;63:901–07.
8. Bellamy N, Campbell J, Robinson V, et al. Intra-articular corticosteroid for treating osteoarthritis of the knee. Cochrane Database of Sys Rev. 2005;2:CD005328.
9. Crossley K, Bennell K, Green S, et al. Physical therapy for patellofemoral pain: a randomized, double-blinded, placebo-controlled trial. Am J Sports Med. 2002;30:857–65.
10. Fransen M, McConnell S, Bell M. Exercise for osteoarthritis of the hip or knee. Cochrane Database Syst Rev. 2003:CD004286.
11. Towheed TE, Maxwell L, Anastassiades TP, et al. Glucosamine therapy for treating osteoarthritis. Cochrane Database of Sys Rev. 2005;(2):CD002946.
Dixit S, Burton M, Mines B. Management of patellofemoral pain syndrome. Am Fam Phys. 2007;75:194–202.
13. Soprano JV. Musculoskeletal injuries in the pediatric and adolescent athlete. Curr Sports Med Rep. 2005;4:329–34.
See Also (Topic, Algorithm, Electronic Media Element)
Algorithms: Knee Pain; Popliteal Mass
- 715.36 Osteoarthrosis, localized, not specified whether primary or secondary, involving lower leg
- 715.96 Osteoarthrosis, unspecified whether generalized or localized, involving lower leg
- 719.46 Pain in joint involving lower leg
- 30989003 Knee pain (finding)
- 33952002 Localized osteoarthrosis (disorder)
- 239873007 osteoarthritis of knee (disorder)
- Knee pain is a common presentation for both acute and chronic injuries.
- Presence of an effusion in a patient younger than 30 years of age signifies a significant knee injury needing accurate/prompt diagnosis.
- Acute mechanism: Consider ligamentous injury, meniscal tear, fracture.
- Overuse mechanism: Consider osteoarthritis, patellofemoral syndrome, tendinopathy, bursitis, and stress fracture.
- Pediatric patient with knee pain: Consider possible physeal, apophyseal, or articular cartilage injuries.