Soft Tissue Knee Injury Workup
- Author: David B Levy, DO, FAAEM; Chief Editor: Trevor John Mills, MD, MPH more...
For patients with significant knee injuries or individuals who may require surgery, appropriate preoperative laboratory investigations might include blood typing and screening and determination of the CBC count and electrolyte, serum glucose, BUN, and creatinine levels.
If warranted by the initial history and physical findings, laboratory analysis of joint aspiration may assist in confirming a diagnosis. Aspirated synovial fluid should be analyzed for WBC count and differential and for glucose and protein levels. Gram staining, cultures, and sensitivity testing should be performed.
A CBC count, erythrocyte sedimentation rate (ESR), and serum glucose and uric acid levels should also be considered at the time of arthrocentesis if infectious or gouty arthritis is a consideration.
Plain images of the knee generally include anteroposterior (AP) and lateral views at minimum. Some centers add 2 oblique projections that are helpful in detecting tibial-plateau fractures. Special views include tunnel view to aid in evaluating the tibial and femoral articular surfaces and a sunrise view to assist in assessing the articular surface and the body of the patella.
Each year, there are over 500,000 visits to the ED for acute knee trauma. Fracture is identified in only 5% of ED knee radiographs. Radiographs are considered the first imaging study for a fall or twisting injury of the knee with focal tenderness, effusion, or inability to bear weight. For a suspected meniscus or ligament tear or injury from a reduced patellar dislocation, MRI is considered the best imaging study. In cases of knee dislocation, patients should undergo radiography, MRI, and angiography.
In most patients with severe ligamentous or meniscal damage, plain radiographic findings are of limited value, and images often appear normal. Fewer than 15% of knee radiographs reveal clinically significant findings.
Various clinical prediction rules exist (Ottawa, Pittsburgh, Weber, Fagan-Davies), with the Ottawa rules being the most validated.
Plain images are recommended for the following scenarios:
Patients older than 55 years (because of an increased risk of pathologic fracture associated with osteoporosis)
Patients with tenderness over the fibular head
Patients with discomfort confined to the patella upon palpation
Patients unable to flex the knee to 90°
Patients incapable of bearing weight, immediately and in the ED, for at least 4 steps
Although plain radiography tends to be unproductive in diagnosing soft-tissue injuries, certain radiographic findings are strongly suggestive of ligamentous, meniscal, or tendon damage. Particularly review the lateral radiograph for fluid within the suprapatellar pouch. The extensor tendon mechanism is normally well outlined. As an effusion accumulates in the suprapatellar pouch, the posterior margin of the quadriceps is apt to be obliterated, and, with additional fluid collecting, the space between the prefemoral and the anterior superior suprapatellar fat pads widens. A cross-table lateral radiograph may expose a fat-fluid level, also known as a lipohemarthrosis, a pathognomonic sign of an intra-articular fracture.
Avulsion fractures of the tibial spine or the femoral condyles imply ligamentous rupture. Occult fractures that are commonly missed on plain radiographs include those of the patellar, tibial plateau, of fibular head, as well as Segond fractures (small vertical avulsion crack of the proximal lateral tibia, also called the lateral capsular sign).
Three radiographic findings associated with anterior cruciate ligament (ACL) injuries are avulsion of the intercondylar tubercle, anterior displacement of the tibia with respect to the femur (labeled the radiographic drawer sign), and a Segond fracture. In a study of 160 patients who had an ACL reconstruction, only 14.4% (23 out of 160) had the correct diagnosis of ACL injury diagnosed on initial presentation at the emergency department or by a general practitioner. The median delay from injury to diagnosis was 13 weeks (0 to 926), and the median total time from injury to surgery was 42 weeks.
Avulsion of the fibular head aligns with lateral collateral ligament (LCL) or biceps femoris injury.
The most common radiographic finding with a posterior cruciate ligament (PCL) injury is avulsion at the site of the ligamentous origin on the posterior tibia.
Unilateral widening of the joint space may denote ligamentous instability.
Chronic medial collateral ligament (MCL) damage, usually lasting longer than 6 weeks, may heal with calcification, presenting as Pellegrini-Stieda syndrome.
Patellar abnormalities can be misleading for an acute fracture. A bipartite or multipartite patella is a normal variant that may be difficult to distinguish from a patellar fracture. An unfused secondary ossification center forming the bipartite patella typically appears in the upper lateral quadrant, tends to occur bilaterally, and reveals well-defined margin lines.
CT scans prove effective for corroborating areas questionable for fracture in the knee region, particularly tibial-plateau fractures in elderly patients.
The relative sensitivity and specificity of clinical examination and MRI findings were comparable (96.5% sensitivity of clinical examination versus 98% of MRI; 87% specificity of clinical examination versus 85.5% of MRI).
MRI has supplanted the arthrography as the procedure of choice for evaluating soft-tissue injuries of the knee. Although MRI plays an important role in future surgical management of acute knee disorders, it is rarely an essential part of the ED workup.
Ultrasonography simplifies differentiation of a Baker cyst, popliteal-artery aneurysm, and thrombophlebitis, and it has also been used to diagnose tendon ruptures. Additionally, sonographic examination can accurately detect effusion of the knee. Ultrasound may prove particularly helpful in aspiration and injection of the knee joint in morbidly obese patients in whom landmark identification may prove difficult. The detection of knee effusion in patients with traumatic knee injury by sonographic examination is highly indicative of internal knee derangement. As experience improves, ultrasonography is a proving to be a useful and inexpensive method of detecting the presence of rupture of the anterior cruciate ligament in the clinical setting of a traumatic hemarthrosis.
An arteriogram is required when a knee dislocation is strongly suspected, even in the absence of reliable signs or symptoms of vascular impairment. Palpation of a regular pulse or Doppler confirmation of pedal pulses does not exclude vascular injury, as intimal tears may be undetectable. The incidence of a concomitant popliteal artery injury is 20-50%. Do not delay emergency surgery for arteriography; imaging can be performed intraoperatively.
Although not 100% sensitive, an injection of methylene blue into the affected knee until the joint is fully distended and observing for extravasations can be done to test for open joint injury.
Knee joint aspiration
Because the knee is the largest synovial joint in the body and given its relatively accessible location, the knee joint provides one of the easiest sites in which to perform arthrocentesis. Indications for knee joint aspiration include confirmation of a diagnosis (The knee is a common site for septic and inflammatory arthritis.) and pain arising from a tense effusion.
Place the patient supine with the knee joint extended, trying to ease any contraction of the quadriceps muscles.
After properly cleansing the skin, infiltrate the skin and underlying dermis with local anesthetic at the point where aspiration will take place.
Approach the joint for aspiration from the medial aspect of the knee, with the site of puncture being 1 cm medial to the anteromedial border of the patella.
Insert an 18-gauge or 20-gauge needle or catheter through the same tract used to inject local anesthetic, at the midpoint or superior position of the patella, aiming for a point between the posterior surface of the patella and the femoral intercondylar notch. The author has found the use of a spinal needle (ie, 21-gauge) to be useful, particularly in obese patients.
Approach the anterolateral border in a similar manner, mirroring the access sites.
Occasionally, the examiner perceives a slight give as the needle perforates the joint capsule.
Aspirate as much fluid as possible, recalling that the knee may contain 50 mL or more of fluid. When the fluid stops flowing freely, compress the suprapatellar pouch and attempt to push additional fluid into the adjacent pouch. If the bore appears obstructed during the arthrocentesis, try rotating the needle or injecting some aspirate, attempting to clear the needle. If this fails, try reinserting the needle one fourth of an inch deeper.
Aspiration of blood indicates a ligamentous tear (eg, ACL, PCL), osteochondral fracture, peripheral meniscus tear, capsular tear, or patellar dislocation.
Presence of fat globules in the aspirant is pathognomonic for an intra-articular fracture.
Hypertrophied synovial tissue or clot formation may hinder aspiration.
Instilling 5-10 mL of 1% lidocaine into the joint and then reexamining the knee may facilitate knee testing.
After withdrawing the needle, dress the iatrogenic puncture wound with an antibiotic ointment and appropriate adhesive sterile dressing.
In the presence of a hot and swollen knee joint, consider the possibility of septic or acute inflammatory arthritis. Joint aspirate should be analyzed for a CBC count with differential, glucose levels, and protein measurements. Also order polarized light microscopy for crystals, and culture and sensitivity testing of the joint fluid. Although rare, infection and hemarthrosis may complicate arthrocentesis.
Gray AM, Buford WL. Incidence of Patients With Knee Strain and Sprain Occurring at Sports or Recreation Venues and Presenting to United States Emergency Departments. J Athl Train. 2015 Nov. 50 (11):1190-8. [Medline].
Kapur S, Wissman RD, Robertson M, et al. Acute knee dislocation: review of an elusive entity. Curr Probl Diagn Radiol. 2009 Nov-Dec. 38(6):237-50. [Medline].
Shah MK. Simultaneous bilateral rupture of quadriceps tendons: analysis of risk factors and associations. South Med J. 2002 Aug. 95(8):860-6. [Medline].
Tuite MJ, Kransdorf MJ, Beaman FD, Adler RS, Amini B, Appel M, et al. ACR Appropriateness Criteria Acute Trauma to the Knee. J Am Coll Radiol. 2015 Nov. 12 (11):1164-72. [Medline].
[Guideline] Pavlov H, Saboeiro GR, Campbell SE, Dalinka MK, Daffner RH, DeSmet AA, El-Khoury GY, Kneeland JB, Manaster BJ, Morrison WB, Rubin DA, Schneider R, Steinbach LS, Weissman BN, Haralson RH III, Expert Panel on Musculoskeletal Imaging. Acute trauma to the knee. [online publication]. Reston (VA): American College of Radiology (ACR); 2005. [Full Text].
Parwaiz H, Teo AQ, Servant C. Anterior cruciate ligament injury: A persistently difficult diagnosis. Knee. 2015 Nov 6. [Medline].
Hurdle MF, Wisniewski SJ, Pingree MJ. Ultrasound-guided intra-articular knee injection in an obese patient. Am J Phys Med Rehabil. 2012 Mar. 91(3):275-6. [Medline].
Shaerf D, Banerjee A. Assessment and management of posttraumatic haemarthrosis of the knee. Br J Hosp Med (Lond). 2008 Aug. 69(8):459-60, 462-3. [Medline].
Akseki D, Ozcan O, Boya H, Pinar H. A new weight-bearing meniscal test and a comparison with McMurray's test and joint line tenderness. Arthroscopy. 2004 Nov. 20(9):951-8. [Medline].
Andersen RE, Crespo CJ, Ling SM, Bathon JM, Bartlett SJ. Prevalence of significant knee pain among older Americans: results from the Third National Health and Nutrition Examination Survey. J Am Geriatr Soc. 1999 Dec. 47(12):1435-8. [Medline].
Arroll B, Goodyear-Smith F. Corticosteroid injections for osteoarthritis of the knee: meta-analysis. BMJ. 2004 Apr 10. 328(7444):869. [Medline].
Bachmann LM, Haberzeth S, Steurer J, ter Riet G. The accuracy of the Ottawa knee rule to rule out knee fractures: a systematic review. Ann Intern Med. 2004 Jan 20. 140(2):121-4. [Medline].
Bahk MS, Cosgarea AJ. Physical examination and imaging of the lateral collateral ligament and posterolateral corner of the knee. Sports Med Arthrosc. 2006 Mar. 14(1):12-9. [Medline].
Berfeld J, Ireland ML, Wojtys EM. Pinpointing the cause of acute knee pain. Patient Care. 1997. 31(18):100-117.
Calmbach WL, Hutchens M. Evaluation of patients presenting with knee pain: Part I. History, physical examination, radiographs, and laboratory tests. Am Fam Physician. 2003 Sep 1. 68(5):907-12. [Medline].
Chandrashekar N, Mansouri H, Slauterbeck J, Hashemi J. Sex-based differences in the tensile properties of the human anterior cruciate ligament. J Biomech. 2006. 39(16):2943-50. [Medline].
Christain EP. Extensor mechanism injuries of the knee. Top Emerg Med. 1995. 17(2):25-35.
Christian SR, Anderson MB, Workman R. Imaging of anterior knee pain. Clin Sports Med. 2006 Oct. 25(4):681-702. [Medline].
Davids JR. Pediatric knee. Clinical assessment and common disorders. Pediatr Clin North Am. 1996 Oct. 43(5):1067-90. [Medline].
Emparanza JI, Aginaga JR. Validation of the Ottawa Knee Rules. Ann Emerg Med. 2001 Oct. 38(4):364-8. [Medline].
Gupta A, Bodin L, Holmstrom B, Berggren L. A systematic review of the peripheral analgesic effects of intraarticular morphine. Anesth Analg. 2001 Sep. 93(3):761-70. [Medline].
Ireland ML. The female ACL: why is it more prone to injury?. Orthop Clin North Am. 2002 Oct. 33(4):637-51. [Medline].
Jackson JL, O'Malley PG, Kroenke K. Evaluation of acute knee pain in primary care. Ann Intern Med. 2003 Oct 7. 139(7):575-88. [Medline].
Jacobson KE, Chi FS. Evaluation and treatment of medial collateral ligament and medial-sided injuries of the knee. Sports Med Arthrosc. 2006 Jun. 14(2):58-66. [Medline].
Karachalios T, Hantes M, Zibis AH. Diagnostic accuracy of a new clinical test (the Thessaly test) for early detection of meniscal tears. J Bone Joint Surg Am. 2005 May. 87(5):955-62. [Medline].
Karistinos A, Paulos LE. "Ciprofloxacin-induced" bilateral rectus femoris tendon rupture. Clin J Sport Med. 2007 Sep. 17(5):406-7. [Medline].
Katz JN, Brophy RH, Chaisson CE, de Chaves L, Cole BJ, Dahm DL, et al. Surgery versus Physical Therapy for a Meniscal Tear and Osteoarthritis. N Engl J Med. 2013 Mar 18. [Medline].
Louden K. Physical therapy as effective as surgery for meniscal tear. Medscape Medical News. March 20, 2013. Available at http://www.medscape.com/viewarticle/781102. Accessed: April 1, 2013.
Munshi M, Davidson M, MacDonald PB, et al. The efficacy of magnetic resonance imaging in acute knee injuries. Clin J Sport Med. 2000. 10(1):34-9. [Medline].
O'Shea KJ, Murphy KP, Heekin RD, Herzwurm PJ. The diagnostic accuracy of history, physical examination, and radiographs in the evaluation of traumatic knee disorders. Am J Sports Med. 1996 Mar-Apr. 24(2):164-7. [Medline].
Perryman JR, Hershman EB. The acute management of soft tissue injuries of the knee. Orthop Clin North Am. 2002 Jul. 33(3):575-85. [Medline].
Richman PB, McCuskey CF, Nashed A, et al. Performance of two clinical decision rules for knee radiography. J Emerg Med. 1997 Jul-Aug. 15(4):459-63. [Medline].
Robertson A, Nutton RW, Keating JF. Dislocation of the knee. J Bone Joint Surg Br. 2006 Jun. 88(6):706-11. [Medline].
Simon LV, Matteucci MJ, Tanen DA. The Pittsburgh Decision Rule: triage nurse versus physician utilization in the emergency department. J Emerg Med. 2006 Oct. 31(3):247-50. [Medline].
Solomon DH, Simel DL, Bates DW, et al. The rational clinical examination. Does this patient have a torn meniscus or ligament of the knee? Value of the physical examination. JAMA. 2001 Oct 3. 286(13):1610-20. [Medline].
Stannard JP, Sheils TM, Lopez-Ben RR, McGwin G Jr, Robinson JT, Volgas DA. Vascular injuries in knee dislocations: the role of physical examination in determining the need for arteriography. J Bone Joint Surg Am. 2004 May. 86-A(5):910-5. [Medline].
Twaddle BC, Bidwell TA, Chapman JR. Knee dislocations: where are the lesions? A prospective evaluation of surgical findings in 63 cases. J Orthop Trauma. 2003 Mar. 17(3):198-202. [Medline].
Wang CY, Wang HK, Hsu CY, Shieh JY, Wang TG, Jiang CC. Role of sonographic examination in traumatic knee internal derangement. Arch Phys Med Rehabil. 2007 Aug. 88(8):984-7. [Medline].