Acute Knee Pain
Clinical Features
Red Flags
- Fracture: history of significant trauma, known osteoporosis or risk factors for same, haematoma, significant pain, positive Ottawa knee rules
- DVT: Acute infection, cancer, stroke or paralysis, previous DVT, CHF, pregnancy, dehydration, varicose veins, nephrotic syndrome, rheumatological disease, IBD, recent major surgery, hormonal treatment, combined oral contraceptives, prolonged immobility or air travel, positive Wells Score.
- Peripheral arterial disease: intermittent claudication, elderly, hypertension, smoking history, CHD, CVD, positive 6 minute walk test, impaired ABPI.
Night pain is often thought of a general red flag symptom. However night pain is very common in hip and knee osteoarthritis, and may not a sole phenomenon of "end-stage OA." [1] In a young adult, child, or older adult with normal plain films, night pain could indicate infection or neoplasm.
A swollen hot knee may indicate infection, however aseptic bursitis and a resolving haemarthrosis can also cause some warmth.
The Wells Score should be used in the appropriate clinical setting of acute non-traumatic knee pain to assess for possibility of DVT.
A patient with a haemarthrosis should be regarded as having internal knee derangement or bony injury until proven otherwise.[2]
History
Physical Examination
Fractures: The tuning fork test for fracture detection may have some validity for ruling out but not ruling in fractures. Place a 128-Hz tuning fork over the bony prominence distal to the suspect fracture. The vibration of the tuning fork is thought to cause the fracture site to move resulting in significant pain.[3]
Vascular Examination: A vascular examination should be performed assessing for distal pulses. If there is suspicion for peripheral vascular disease then perform an ankle brachial pressure index (ABPI) measurement.
Imaging
Plain Films
Ottawa knee rules are 100% sensitive for fractures. A knee series is required with any of the following findings
- Age 55 or order OR
- Isolated tenderness of the patella (no bone tenderness of knee other than patella) OR
- Tenderness of the head of the fibula OR cannot flex to 90 degrees OR
- Unable to bear weight both immediately and in the emergency room department for 4 steps (unable to transfer weight twice onto each lower limb regardless of limping)
Treatment
- ↑ Woolhead et al.. Night pain in hip and knee osteoarthritis: a focus group study. Arthritis care & research 2010. 62:944-9. PMID: 20191575. DOI.
- ↑ Maffulli et al.. Acute haemarthrosis of the knee in athletes. A prospective study of 106 cases. The Journal of bone and joint surgery. British volume 1993. 75:945-9. PMID: 8245089. DOI.
- ↑ Toney et al.. Using Tuning-Fork Tests in Diagnosing Fractures. Journal of athletic training 2016. 51:498-9. PMID: 27384015. DOI. Full Text.
