Evaluation of knee injury

Open fractures

As with any fracture, whether open or closed, it is important to assess the neurovascular status of the affected limb. The initial assessment should include:

• palpation of the dorsalis pedis and posterior tibial pulses

• light touch sensation over the first dorsal web space and lateral foot for the common peroneal nerve

• light touch sensation over the plantar aspect of the foot and medial instep for the tibial nerve

• assessment of motor function of the distal leg.

An open fracture is a surgical emergency. Administer prophylactic antibiotics and, if needed, tetanus prophylaxis on presentation. Surgical irrigation and debridement should be performed within the first few hours.

Patients with vascular compromise need immediate referral and assessment by a traumatologist or vascular surgeon. Fractures should be immobilized and orthopedic consultation obtained.

Knee dislocations

Dislocated or spontaneously reduced knee dislocations require urgent evaluation due to the high risk of associated vascular or neurologic injury.

CT angiograms are indicated for any cases of decreased pulses or high-velocity knee dislocation.

Open knee dislocations need assessment as to whether reduction in the emergency department or operating room is necessary.

Popliteal artery tears constitute a surgical emergency. The amputation rate exceeds 90% if a limb is not revascularized within 8 hours.[5]Green NE, Allen BL. Vascular injuries associated with dislocation of the knee. J Bone Joint Surg Am. 1977 Mar;59(2):236-9. http://www.ncbi.nlm.nih.gov/pubmed/845209?tool=bestpractice.com Popliteal artery intimal flap tears must be carefully evaluated for a minimum of 72 hours post-injury because a clot may form in the popliteal artery and block blood flow.

Knee dislocations and revascularized limbs after knee dislocation must be carefully monitored for the possible development of compartment syndrome.

Septic arthritis

Patients with significant pain, redness, warmth, and swelling around the knee must be evaluated to exclude septic arthritis.

Patients with these symptoms and signs may include those who have had recent surgery and those who have had recent open fractures or lacerations around the knee.

Initial investigations include blood cultures (if the patient is febrile), blood tests, x-rays and joint aspiration.

Anterior-posterior x-rays may be normal. Erythrocyte sedimentation rate and C-reactive protein are likely to be elevated. Aspiration of the joint under sterile conditions can differentiate between bacterial infection, gout, or pseudogout. Analysis of the aspirated fluid should include aerobic and anaerobic cultures, cell count and differential, analysis for crystals, and a Gram stain.