2.3 Intra-Articular Injections & Joint Preservation Interventions

2.3 Intra-Articular Injections & Joint Preservation Interventions

Core Clinical Scope: When conservative non-pharmacologic and oral therapies fail to provide adequate pain relief in osteoarthritis, intra-articular injection modalities (corticosteroids, viscosupplementation, and orthobiologics) and joint-preserving realignment surgeries (such as high tibial osteotomy) offer targeted local management. Orthopaedic nurses must master the pharmacodynamics, dosing ceilings, potential complications, patient selection criteria, and post-procedural surveillance protocols for each modality.

---

Intra-Articular Corticosteroid (IACS) Injections

Intra-articular corticosteroid injections remain one of the most widely performed procedural interventions for acute osteoarthritic joint flares associated with synovial effusion and inflammatory synovitis.

Mechanism of Intra-Articular Corticosteroids:
Intra-Articular Injection (e.g., Triamcinolone Acetonide / Methylprednisolone)
   ↓
Glucocorticoid Receptor Binding → Downregulation of NF-κB Transcription
   ↓
Profound Suppression of Pro-Inflammatory Cytokines (IL-1β, TNF-α, COX-2, Prostaglandin E2)
   ↓
Decreased Synovial Vascular Permeability & Capillary Leak → Rapid Resolution of Joint Effusion
   ↓
Analgesic Onset within 24 to 48 Hours │ Duration of Benefit: 2 to 6 Weeks (Rarely up to 12 Weeks)

Formulations & Extended-Release Options

• Standard Suspensions: Triamcinolone acetonide (Kenalog-40, 20–40 mg) and methylprednisolone acetate (Depo-Medrol, 40–80 mg), typically co-administered with a local anesthetic (e.g., 1% lidocaine or 0.5% bupivacaine) for immediate diagnostic and short-term anesthetic relief.
• Extended-Release Microspheres: Triamcinolone acetonide extended-release injectable suspension (Zilretta) utilizes a poly(lactic-co-glycolic acid) [PLGA] matrix to provide sustained intra-articular micro-dosing over 12 weeks while attenuating systemic glucocorticoid exposure.

Chondrotoxicity Risks & Annual Injection Limits

Although corticosteroids provide potent short-term anti-inflammatory analgesia, laboratory and prospective clinical studies (including landmark randomized trials by McAlindon et al., JAMA) demonstrate that repeated intra-articular steroid injections induce dose- and frequency-dependent chondrotoxicity. Glucocorticoids inhibit chondrocyte proteoglycan synthesis, induce chondrocyte apoptosis, and accelerate articular cartilage volume loss.

Critical Clinical Guideline: Routine clinical practice mandates capping intra-articular corticosteroid injections to no more than 3 to 4 injections per individual joint per year, maintaining a minimum interval of 3 months between injections into the same joint.

Systemic Side Effects & Glycemic Management in Diabetes

Despite localized intra-articular administration, up to 80% of the injected steroid dose enters systemic circulation through synovial capillary absorption:

• Transient Hyperglycemia: Diabetic patients frequently experience substantial blood glucose elevations (often surging to 200–400 mg/dL), typically starting within 4 to 12 hours post-injection and persisting for 48 to 72 hours (up to 5 days).
• Nursing Action: Educate diabetic patients to perform increased blood glucose monitoring (at least 3 to 4 times daily for 72 hours), review insulin or oral hypoglycemic titration plans with their primary care provider or endocrinologist, and establish emergency contact thresholds for persistent hyperglycemia (>300 mg/dL with ketones).
• Other Systemic Reactions: Transient facial flushing (occurring in 10% to 15% of patients within 24–48 hours), transient hypothalamic-pituitary-adrenal (HPA) axis suppression, and mild fluid retention.

Post-Injection Flare vs. Septic Arthritis

Orthopaedic nurses must clearly distinguish between a benign, self-limiting chemical reaction and a catastrophic intra-articular infection:

---

Viscosupplementation / Intra-Articular Hyaluronic Acid (HA)

Endogenous hyaluronic acid (hyaluronan, HA) is a high-molecular-weight glycosaminoglycan (4 to 10 MDa) synthesized by Type B synovial cells. In healthy joints, HA imparts high elastoviscosity to synovial fluid, facilitating boundary lubrication, shock absorption, and chondroprotection. In osteoarthritis, intra-articular HA concentration and molecular weight are reduced by 50% to 67%.

Viscosupplementation Mechanism & Therapeutic Kinetics:
Exogenous Intra-Articular Hyaluronan Administration
   ↓
Restoration of Synovial Fluid Elastoviscosity & Boundary Lubrication
   ↓
CD44 & RHAMM Receptor Activation on Chondrocytes and Synoviocytes
   ↓
Downregulation of IL-1β-Mediated MMP Expression + Stimulation of Endogenous High-MW HA Synthesis
   ↓
Delayed Analgesic Onset: Peaks at 4 to 12 Weeks │ Therapeutic Benefit: Sustained up to 24 Weeks (6 Months)

Formulations & Clinical Considerations

• Non-Cross-Linked Formulations: Low-to-medium molecular weight (e.g., sodium hyaluronate [Hyalgan, Supartz]; 500–1,200 kDa), administered as a series of 3 to 5 weekly injections.
• Cross-Linked Formulations: High molecular weight (e.g., hylan G-F 20 [Synvisc-One]; 6,000 kDa), administered as a single high-volume injection or 3-injection series.
• Pseudoseptic Reaction: Cross-linked formulations carry a distinct risk (1% to 3%) of an acute severe sterile inflammatory reaction (pseudoseptic arthritis), characterized by massive sterile joint effusion 24 to 72 hours after injection (especially during repeat injection courses). Synovial fluid aspiration is mandatory to rule out bacterial infection.
• Guideline Consensus: Professional society recommendations are variable. While the ACR conditional guidance advises against routine HA use due to variable effect sizes in clinical trials, the AAOS provides a moderate/conditional recommendation for select patients with symptomatic knee OA who have failed initial conservative therapies.

---

Platelet-Rich Plasma (PRP) & Orthobiologics Evidence

Platelet-Rich Plasma is an autologous biologic therapy prepared by centrifuging whole blood to concentrate platelets 2 to 8 times above baseline physiological levels.

• Biological Mechanism: Platelet alpha-granules degranulate upon intra-articular injection, releasing a rich milieu of bioactive growth factors, including Transforming Growth Factor-beta (TGF-β), Platelet-Derived Growth Factor (PDGF), Vascular Endothelial Growth Factor (VEGF), and Fibroblast Growth Factor (FGF). These factors suppress NF-κB signaling, antagonize IL-1β, downregulate catabolic enzymes, and stimulate ECM matrix synthesis.
• Leukocyte-Poor vs. Leukocyte-Rich Formulations:
  • Leukocyte-Poor PRP (LP-PRP): Preferred for intra-articular knee OA. Minimizing neutrophils reduces the release of pro-inflammatory metalloproteinases and reactive oxygen species, resulting in fewer post-injection inflammatory flares.
  • Leukocyte-Rich PRP (LR-PRP): Contains elevated neutrophil concentrations, which can exacerbate synovial inflammation; primarily reserved for extra-articular chronic tendinopathies.
• Evidence & Clinical Utility: High-level meta-analyses indicate that LP-PRP provides statistically significant improvements in WOMAC pain and functional scores at 6 to 12 months compared to hyaluronic acid or saline in patients with mild-to-moderate (Kellgren-Lawrence Grades 1 to 3) knee OA.

---

Joint Preservation Surgery: High Tibial Osteotomy (HTO)

In younger, physically active individuals with isolated unicompartmental osteoarthritis, total joint replacement may fail prematurely due to accelerated polyethelene wear and aseptic loosening. High Tibial Osteotomy (HTO) is the premier joint-preserving surgical intervention designed to realign the mechanical weight-bearing axis of the lower extremity.

Biomechanical Rationale of High Tibial Osteotomy (HTO):

[Preoperative State: Varus Deformity]
Mechanical Axis passes through Medial Compartment (75-80% Load Concentration)
   ↓ Accelerates Medial Cartilage Eburnation & Subchondral Sclerosis

[Surgical Intervention: Valgus Realignment Osteotomy]
Medial Opening-Wedge (with Plate + Bone Graft) OR Lateral Closing-Wedge Osteotomy
   ↓ Realignment shifts Mechanical Axis across Tibial Plateau into Lateral Compartment (Fujisawa Point ~62%)

[Postoperative Result]
Offloads Diseased Medial Hyaline Cartilage → Postpones Total Knee Arthroplasty (TKA) by 5 to 10+ Years

Patient Selection Criteria for High Tibial Osteotomy

Patient selection is the primary determinant of long-term success following HTO:

Postoperative Nursing Care & Complications Surveillance

1. Weight-Bearing & Bracing Protocols: Patients are maintained strictly non-weight-bearing (NWB) or touch-down weight-bearing (TDWB) with a hinged knee brace locked in extension for 6 to 8 weeks until radiographic confirmation of bony union at the osteotomy site.
2. Neurovascular Monitoring (Peroneal Nerve): The common peroneal (fibular) nerve courses around the fibular neck in close anatomical proximity to the lateral proximal tibia. Frequent neurovascular assessments must specifically test:
   • Motor: Active dorsiflexion of the great toe and ankle (deep peroneal nerve).
   • Sensory: Light touch sensation in the first dorsal web space (deep peroneal nerve) and the lateral dorsum of the foot (superficial peroneal nerve).
3. Thromboprophylaxis: Administer chemical anticoagulation (e.g., low-molecular-weight heparin, direct oral anticoagulants, or aspirin) and mechanical compression devices (sequential compression devices [SCDs]) to prevent deep vein thrombosis (DVT).
4. Bone Union Surveillance: Monitor for signs of delayed union or nonunion at the osteotomy site, including persistent focal tenderness, abnormal motion, or lack of bridging callus on serial plain radiographs.