Knee Arthrocentesis or Knee Joint Aspiration

Last Updated on November 13, 2019

Knee arthrocentesis refers to puncture of the knee joint and the aspiration of its synovial fluid. It is used for synovial fluid analysis to aid in diagnosis and also for therapeutic purposes.

Knee joint can be approached by multiple approaches [discussed below]

Knee Joint Aspiration or knee arthrocentesis — Knee Joint Aspiration, Image credit: orthosports

Indications of Knee Arthrocentesis

Diagnosis

Acute monoarticular [that affects a single joint] arthritis
Suspected infection (eg, septic arthritis)
Inflammatory joint effusion
- Gout
- Pseudogout
- Rheumatologic disorders
- Reactive arthropathies

Therapeutic

To relieve a large painful effusion.
Instillation of medications
Repeated arthrocentesis for septic arthritis in carefully selected patients as a means of decreasing bacterial load

Contraindications

Cellulitis in the overlying skin
Overlying skin lesions (eg, dermatitis or psoriasis)
Known bacteremia
Bleeding disorders
Patient on anticoagulation medication

Procedure of Knee Aspiration or Knee Arthrocentesis

Different Approaches

Knee joint aspiration can be done via a parapatellar approach (usually preferred), a suprapatellar approach, or an infrapatellar approach.

Parapatellar Approach

The knee can be approached from the medial side or lateral side. The insertion site is just below the midpoint of either the medial or the lateral border of the patella. The needle is directed inferomedially. The needle is kept perpendicular to the long axis of the femur and points toward the intercondylar notch of the femur.

Suprapatellar Approach

This approach accesses the joint from the superior aspect. It can be done from the midpoint of either the superomedial or the superolateral border of the patella. The needle is directed toward the intercondylar notch of the femur.

Infrapatellar Approach

In this approach, the needle is inserted about 5 mm below the inferior border of the patella and just lateral to the edge of the patellar tendon. Piercing of patellar tendon should be avoided with this approach.

Procedure

Determine the site of needle insertion. This would depend on the approach chosen.
Prepare the skin with a sterile solution and drape the part.
Attach the 18- or 20-gauge needle to the 20-mL syringe. In larger effusions, 50-60 ml syringes may be used. Otherwise, an extra syringe should be kept handy, just in case.
Stretch the skin between two fingers and insert the needle into the joint while keeping a gentle pull on the plunger. Placement of a towel under the popliteal region to flex the knee to 15-20° may facilitate entry by opening up the joint space.
Readjust the direction of the needle if it strikes the bone.
If the needle is in the joint, the fluid would start entering the syringe. Milking the region could help in case the flow is slow.
Once aspiration is complete, the needle is removed and a bandage applied.

Complications of Knee Arthrocentesis

Dry Tap

This can be caused by

improper needle placement
A small amount of effusion
Mechanical obstruction of the needle against cartilage or thickened synovium

Cartilage Injury

This is minimal with smaller bore needles.

Hemarthrosis

Most hemarthroses are small and self-limited. Correction of coagulopathy may be desired if that is the reason for hemarthrosis.

Infection

It is rare. If there appears a higher risk of infection, prophylactic antibiotics may be started.

About Dr Arun Pal Singh

Arun Pal Singh is an orthopedic and trauma surgeon, founder and chief editor of this website. He works in Kanwar Bone and Spine Clinic, Dasuya, Hoshiarpur, Punjab.

This website is an effort to educate and support people and medical personnel on orthopedic issues and musculoskeletal health.

You can follow him on Facebook, Linkedin and Twitter

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