The heel tap test is used to detect what condition when pain is elicited in the knee area?

• A. Joint effusion or irritation (septic knee)
• B. ACL tear
• C. Osteoarthritis
• D. Medial meniscal tear

Answer: (A)

Tapping the heel assesses whether there is knee joint effusion or intra-articular irritation. The percussion sends a small shock through the leg into the knee, and if fluid or inflamed synovium is present, the distended joint capsule is tender and the patient experiences knee pain. This makes the heel tap test a quick way to indicate an effusion, which can occur with septic arthritis or other inflammatory processes inside the joint.

ACL tears are diagnosed with stability and provocative tests (like Lachman or anterior drawer) and present with instability rather than a heightened pain response to percussion. Osteoarthritis typically shows chronic, possibly crepitus-filled joint pain with stiffness and limited ROM rather than a pain provoked specifically by tapping. Medial meniscal tears tend to produce joint line tenderness and reproduce pain with specific maneuvers such as McMurray or Thessaly tests, rather than a percussion-induced knee pain.