How do symptoms of a superficial wound infection differ from a deep prosthetic joint infection?

1. What clinicians mean by “superficial” vs “deep/PJI”

Superficial surgical-site infection is defined as infection confined to the skin and subcutaneous tissues of the incision without extension deep to the fascia; deep PJI is defined as infection involving the prosthetic cavity or joint space itself ^{[2] [3]}. This anatomical distinction matters because superficial infections may be treated conservatively, whereas infections that reach the prosthesis usually require more aggressive interventions including surgery ^{[1] [5]}.

2. How symptoms differ at the incision and joint

Superficial infection typically shows local wound findings—purulent drainage, erythema around the incision, localized pain and possibly a positive wound swab—usually recognized in the early postoperative period ^{[6] [1]}. By contrast, deep PJI often manifests primarily as joint-centered complaints: persistent or new-onset joint pain, swelling, stiffness and limited motion; a sinus tract or ongoing wound drainage over the prosthesis is a strong PJI sign ^{[5] [7]}.

3. Systemic signs and why they can be absent in PJI

Although textbook infections cause fever and leukocytosis, deep prosthetic infections frequently lack these systemic signs—fever, leukocytosis and sepsis are often absent—because a prosthesis lowers the microbial load needed for infection and biofilm formation blunts overt systemic inflammatory responses ^{[4] [8]}. The absence of fever or bloodwork abnormalities does not rule out a deep infection ^{[4] [5]}.

4. Timing: early vs late presentations and diagnostic challenges

Superficial wound infections commonly present within days to a few weeks after surgery; deep infections can be early or late and may present months or even years later with chronic joint pain without prior wound problems ^{[9] [3]}. Early postoperative superficial infection and early PJI can look similar, and several authors emphasize that it is difficult to differentiate superficial wound infection from early post‑operative PJI, making prompt assessment important ^[10].

5. Why a superficial infection can be a red flag

Superficial wound problems—hematoma, wound drainage or dehiscence—are documented risk factors for progression to deep PJI because contiguous spread can occur across incompletely healed fascial planes ^{[11] [12]}. Guidelines therefore highlight that persistent wound drainage or a sinus tract over a prosthesis should raise strong suspicion for PJI ^{[7] [8]}.

6. Diagnostic steps and where each sign matters

A local wound swab may reflect skin colonization and is discouraged for diagnosing deep infection; cultures from joint aspiration or deep tissue are more informative for PJI ^[8]. Clinical clues—sinus tract, persistent drainage, acute painful prosthesis or unexplained chronic pain—are used to decide when to pursue joint aspiration, imaging and specialist tests that distinguish superficial from deep infection ^{[7] [5]}.

7. Treatment implications tied to differing presentations

Superficial infections are often managed with antibiotics and local wound care if truly confined to soft tissue; infections that extend to the implant typically require surgical intervention plus prolonged antibiotics, because biofilm protects organisms on prosthetic surfaces ^{[1] [5]}. Multiple sources warn that treating presumed superficial inflammation with prolonged antibiotics without addressing a possible deep infection risks treatment failure ^[10].

8. Limitations and practical takeaways

Available sources consistently stress diagnostic ambiguity early after surgery—superficial and early deep infections can overlap clinically—so clinicians rely on pattern recognition (wound vs joint-centered symptoms), timing, and targeted microbiology to differentiate them ^{[10] [9]}. If there is persistent wound drainage, new or worsening joint pain, a sinus tract, or concern about progression, current guidelines recommend evaluation for PJI rather than assuming a confined superficial wound infection ^{[7] [8]}.