Knee Pain

Knee Pain

Knee pain is a common sick call complaint with a broad differential diagnosis.  It is important to differentiate in the history how the knee became painful.  Based on the mechanism of injury, one can narrow the possible diagnoses into a working differential diagnosis, further refined using the history and physical.

Differential diagnosis of knee pain

Trauma /acute

• Fracture

• Internal Derangement

• Meniscal injury (most common)

• Ligamentous injury – Anterior Cruciate (ACL), Posterior Cruciate (PCL),

• Medial Collateral (MCL), and Lateral Collateral (LCL)

• Knee dislocation (multiple ligamentous tears and unstable knee)

• Pre patellar Bursitis                                    

• Patellar Dislocation (not to be confused with knee dislocation)      

Overuse/chronic

• Patellofemoral Syndrome (PFS)

• Iliotibial Band Syndrome (ITBS)

• Degenerative joint disease (DJD)  (Osteoarthritis)

• Stress fractures

• Meniscal tears (if missed acutely)

• Patellar tendonitis

• Osteochondritis Dessicans (OCD) and loose bodies

Infection/ acute arthritis

• Septic joint  - GC, Lyme, TB, etc.

• Gout/pseudogout

History 

This will narrow the focus.  Key historical points include: 

• Mechanism of injury

• Location of pain, noise or other sensations

• Ability to bear weight

• Location and rapidity of swelling

• Giving way – mechanical instability vs. guarding from pain

• Locking- unable to move leg unless physically manipulate it to unlock it.

Trauma

• Fracture

  • High-impact direct blow

  • Inability to bear weight

  • Heard a snap

  • Immediate swelling and ecchymosis

  • Obvious deformity

• Meniscal injury

  • Twisted knee on planted, weight bearing foot

  • Delayed swelling (12-24 hours)

  • Locking, clicking, giving way

• ACL tear

  • Cut or pivot

  • Heard a pop

  • Inability to continue activity – knee unstable – gives way

  • Immediate swelling (2-4 hours secondary to hemarthrosis)

• Knee dislocation

  • Trauma causing multiple ligament disruption

  • Unable to bear weight, severe pain and deformity

• Other ligamentous injuries

  • Valgus injury (knee bends toward midline) – MCL

  • Varus injury – rare – LCL

  • Hyperextension or direct blow – PCL

• Prepatellar bursitis

  • Often got direct blow to anterior knee

  • Not painful to move joint

• Patella dislocation/subluxation

  • Felt and heard a pop

  • If truly dislocated, almost all lateral, reduced by straightening leg

Overuse Injuries can often be distinguished by their location and character of pain

• PFS            

  • Anterior knee pain

  • Worse going down stairs

  • Worse with prolonged sitting

• ITBS            

  • Lateral knee pain

  • Worse with running on slanted surfaces (e.g. a beach)

• DJD            

  • Achy pain throughout

  • Often worse medially

  • Worse later in day

• Stress fractures   

  • Pain initially after activity

  • Gradually increases  

  • Femoral shaft  stress fractures often present with deep achy knee pain

• Meniscal tears – if missed acutely

  • Achy pain one side or the other

  • Painful click and locking

• Loose bodies

  • Often from OCD

  • Locking

  • Achy pain

Septic Joint

• A surgical emergency and should be treated as such.  

• The patient will have a very painful active and passive Range of Motion (ROM).  

• They may also have erythema and a fever.

Physical exam:

• Observe for edema (swelling outside/around the joint), erythema

• Palpate the knee. 

• Feel for an effusion.  An effusion will be due to one of three things and represents intraarticular pathology.  Tapping the knee is indicated for ruling out infection and to relieve pain.  If you do not suspect infection and the patient’s knee is not painful due to a tense effusion, you do not need to tap.

  • Reactive – clear fluid due to DJD, etc

  • Inflammatory – infection, crystal disease – has WBCs

  • Bloody – tear in structures such as ligaments, meniscus, bone (look for fat)

• Perform specific maneuvers

  • Lachman – for ACL tear

  • McMurray’s, joint line tenderness, flick and duck walk – meniscus

  • Diffuse medial or lateral tenderness, check for stability at 0 and 30 degrees

  • Check for patellar signs: Quad inhibition and patellar compression for PFS, Patellar apprehension for dislocation/subluxation

  • Palpate patellar tendon for signs of tendonitis

  • Check distal pulses and sensation – may have vascular injury e.g. with dislocated knee

When are x-rays needed? 

Trauma- Ottawa Rules 

• Age 55 or older

• Isolated tenderness of the patella

• Tenderness at the head of the fibula

• Inability to flex the knee to 90 degrees

• Unable to bear weight (2 steps with affected leg) both immediately and upon evaluation

• Suspected OCD

  • Obtain tunnel view, A/P and lateral

  • If positive, obtain the contralateral side.  (Can be bilateral)

• Suspected ACL tear

• R/O intra-articular fractures – tibial spine

• R/O Segond fracture (very small avulsion fracture of the lateral tibial plateau)

• Patellar dislocation- R/O fracture after relocation

• Multiple visits without improvement

• Atypical presentation

• R/O arthritis

When is MRI needed?

• To evaluate soft tissue injuries – meniscus, ACL, PCL

• Staging of OCD

• Note:  MRI is not necessary to confirm diagnosis.  For example, a patient with suspected meniscal tear by history and physical can be treated as such. 

  When is arthrocentesis beneficial?

• To aid in diagnosis

• Mandatory when suspecting infection

  • Cell count

  • Glucose

  • Protein

  • Gram Stain

  • Culture

• R/O gout or pseudo gout

• Crystal analysis

• To provide symptomatic relief

• Trauma

• To improve examination – relieves tension and can inject lidocaine

What if exam is not accurate secondary to patient pain and guarding?

• If significant ligamentous disruption is suspected and rapid diagnosis is necessary can do arthrocentesis and inject joint with local anesthetic and repeat exam.
                   OR

• Treat patient conservatively and repeat exam in two weeks after acute pain subsides.

When should I refer emergently?

• Suspected or confirmed septic joint

• Infected prepatellar bursitis not responding to oral antibiotics

• Knee dislocation (disruption of multiple ligaments) – vascular status may be compromised

• Locked knee that can not be unlocked

• Suspected or confirmed intra-articular fractures

• Inability to extend leg (patellar tendon rupture, fractures)            

Management

• Recognize emergencies

• Septic joint

  • Immediate orthopedic referral for surgical drainage and antibiotics

  • If unable to Medevac, antibiotics – ceftriaxone and medevac at earliest possible time

• Patella dislocation

  • Lateral pressure against patella while extending knee

  • 3 weeks of immobilization at 30 degrees of flexion, quad strengthening

• Locked joint (meniscus, OCD, loose body)

  • R/O pseudolocking (hamstring spasm, swelling)

  • If unable to unlock joint, consider injecting local anesthetic and performing ROM.  Make sure you are not making an intra-articular fracture worse.

• Knee dislocation – relocate and check distal pulses – can tear popliteal vessels – surgical emergency

• Acute trauma.  If no x-ray or other diagnostic capabilities available, follow acute trauma guidelines until able to perform.  Often, as with internal derangement, definitive diagnosis may be delayed until acute effusion and pain have resolved.

 Acute management - PRICEMM

• Protection - Range of motion bracing

• Rest - May require crutches if significant pain or instability with weight bearing. 

• Ice – 20 minutes t.i.d.

• Compression – Ace wrap may help control excess edema

• Elevate – above heart if possible

• Meds - NSAIDS for pain and inflammation

• Modalities – electrical stimulation may help reduce pain and inflammation

After acute pain resolves, obtain definitive diagnosis and continue appropriate rehabilitation

• Range of motion

• Strengthening

• Endurance

Overuse Injuries

• Relative rest

• Ice 

• NSAIDS

• Physical therapy

• Orthopedic referral if conservative treatment fails

Sharon Burnham, DO, and Scott D. Flinn, MD

For further information, read:

Sports Related Injury Management, in the General Medical Officer Manual

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*This web version is provided by The Brookside Associates, LLC.  It contains original contents from the official US Navy NAVMED P-5139, but has been reformatted for web access and includes advertising and links that were not present in the original version. The medical information presented was reviewed and felt to be accurate in 2001. Medical knowledge and practice methods may have changed since that time. Some links may no longer be active. This web version has not been approved by the Department of the Navy or the Department of Defense. The presence of any advertising on these pages does not constitute an endorsement of that product or service by either the US Department of Defense or the Brookside Associates. The Brookside Associates is a private organization, not affiliated with the United States Department of Defense.

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