3-75
more rarely meniscal tear) Does the knee lock or catch? (suggests meniscal tear, loose body, or ACL tear
with stump “catching” in joint) Did you hit your knee on something or have you been crawling on your
knees? (suggests prepatellar bursitis) Can you walk and/or bear weight? (inability suggests fracture or knee
dislocation)
Objective: Signs
Using Basic Tools: Inspection: Look for swelling, erythema, bruising, ambulation and full range of active
motion.
Palpation: Compare knees throughout exam for temperature differences (increased warmth suggests infection
or prepatellar bursitis). Note any swelling in the joint (trauma [blood] or inflammation [gout, arthritis, infection
or reactive effusion from PFS]). Perform passive range of motion with hand on knee feeling for abnormal
limitations in motion, clicking or popping (cartilage, ligament or meniscal injury). Perform Lachman (drawer)
test for ACL and posterior sag test for posterior cruciate ligament (PCL) to indicate tears of the respective
ligaments. Assess meniscal integrity (tears cause joint line tenderness, effusion, and positive McMurray sign
[pain with passive extension of knee while externally rotated]). Palpate the collateral ligaments. If tender, bend
the knee medially and laterally at 0 and 30° of flexion (increased opening suggests tear). Palpate patella
(apprehension suggests patellar dislocation or subluxation). Evaluate mobility of patella (PFS) by pushing
it medially and laterally while quadriceps is flexed. Feel the patellar tendon for intactness and tenderness
(rupture or tendinitis). Assess distal pulses.
Using Advanced Tools: Lab: CBC and Gram stain of aspirated joint fluid to rule out infection; Urinalysis: urate
crystals in sediment under polarized light microscopy in gout; X-ray: For fractures, dislocations, alterations
of joint space.
Assessment:
Differential Diagnosis
Acute traumatic knee pain can be due to damage to ligaments (ACL, PCL, MCL, LCL), bone (fracture or
osteochondral defect), muscle (quadriceps tear), cartilage (meniscal tear) or capsule (patellar subluxation or
dislocation).
Infection and other inflammatory conditions (gout) often present acutely.
Chronic knee pain may be due to an old untreated injury, PFS, iliotibial band syndrome (ITBS), arthritis,
tendonitis, bursitis or stress fractures.
Plan:
Treatment
- If patient unable to walk, use crutches, cane and/or splint (may be field expedient).
- Reduce/inhibit swelling in the injured joint: Rest, ice, compression (wrap, brace or splint), elevation (RICE).
- Use NSAIDs as necessary for pain and inflammation. For severe pain, see Procedure: Pain Assessment
and Control. - Gonococcal arthritis is the most likely cause of infection in an otherwise intact knee without a history of
trauma. If septic arthritis is suspected, treat with ceftriaxone 1 gm IV or IM q 24h until systemic symptoms are
clearly resolving. Then, continue therapy for least 7 days with cefixime 400mg bid or ciprofloxacin 500mg
bid. Because of high probability of simultaneous infection with chlamydia trachomatis as an STD, treat with
azithromycin 1 gm po in a single dose, or doxycycline 100 mg po bid x 7 days - Aspirate pus/fluid and consider injecting anesthetic to enable member to walk out in combat conditions
(see Procedure: Joint Aspiration). Injecting steroids is contraindicated--steroids may allow infection to rapidly
worsen.
Patient Education
General: Unless truly catastrophic, most knee injuries will resolve through conservative treatment, rehabilita-
tion and/or laparoscopic surgery.
Activity: Depending on severity of injury, gradually advance range of motion, then add strength program
with weight bearing as tolerated.
Medications: Any medicine may cause an allergic reaction. NSAIDs may cause bleeding ulcers, kidney
and liver damage.