2.2 Lower Extremity Conditions & Post-Op Protocols
Key Takeaways
- Posterior total hip arthroplasty (THA) precautions: no hip flexion past 90 degrees, no adduction past midline, no internal rotation; the anterior approach restricts extension, external rotation, and adduction.
- Total knee arthroplasty (TKA) ROM benchmarks: about 90 degrees flexion by week 2, 110-115 by week 6, and full active extension to 0 degrees as early as possible to prevent flexion contracture.
- Meniscus repair generally requires non-weight-bearing (NWB) to toe-touch weight-bearing (TTWB) for 4-6 weeks with brace-limited flexion; partial meniscectomy is weight-bearing as tolerated (WBAT) immediately.
- Anterior cruciate ligament reconstruction (ACL-R) progresses protective (weeks 0-2), motion/strength (weeks 2-12), running (months 3-5), and return-to-sport (months 6-9+) with limb symmetry index (LSI) >90%.
- Ankle sprain grades: I (microtear, full weight-bearing early), II (partial tear, brace + protected weight-bearing), III (complete tear, immobilization 2-4 weeks before progressive loading).
Hip Conditions
Total Hip Arthroplasty (THA) Precautions by Approach
The surgical approach dictates which motions threaten the repair, and the NPTE-PTA tests both common patterns. Precautions typically apply for the first 6-12 weeks while the soft-tissue envelope heals.
| Approach | Forbidden Motions (Typical 6-12 weeks) | Common PTA Modifications |
|---|---|---|
| Posterior (posterolateral) | No hip flexion >90 degrees; no adduction past midline; no internal rotation (IR) | Elevated toilet seat, abduction pillow in supine, long-handled reacher/sock aid; avoid low chairs and crossing legs |
| Anterior (direct anterior) / anterolateral | Avoid combined hip extension + external rotation (ER); avoid adduction past midline | Limit aggressive backward stepping and early bridging into extension |
Worked scenario: A posterior-THA patient sitting at the bed edge wants to bend forward to don socks. Bending forward flexes the hip past 90 degrees, so the PTA hands over a long-handled sock aid and reacher and reviews precautions. Hip osteoarthritis without surgery is managed with progressive resistance, aquatic exercise, gait training with an assistive device for antalgic gait, and activity pacing.
Knee Conditions
Total Knee Arthroplasty (TKA)
The biggest enemy of a TKA outcome is a flexion contracture, so recovering full extension to 0 degrees is prioritized alongside flexion.
| Week | Flexion Goal | Extension Goal | Typical Intervention |
|---|---|---|---|
| 1 | 70-90 degrees | -5 to 0 degrees | Heel slides, prone hangs, quad sets, ankle pumps |
| 2-3 | 90-105 degrees | 0 degrees | Stationary bike (partial then full revolution), short-arc quad |
| 4-6 | 110-115 degrees | 0 degrees | Step-ups, mini-squats, terminal knee extension |
| 8-12 | 115-125 degrees | 0 degrees | Progressive resistance, balance, community ambulation |
A patient stuck at -10 degrees of extension (a 10-degree flexion contracture) at week 4 needs low-load prolonged extension positioning (prone hangs, towel under heel) and prompt PT communication — a residual contracture impairs gait permanently.
ACL Reconstruction (ACL-R)
Criterion-based phasing:
- Phase I (0-2 weeks): Protect the graft; restore full passive extension; quad activation; weight-bearing as tolerated (WBAT) with the brace locked at 0 degrees per surgeon.
- Phase II (2-12 weeks): ROM restoration, closed-chain strengthening (mini-squats, leg press in a safe arc), proprioception. Avoid open-chain knee extension 0-30 degrees through about 12 weeks because of anterior shear on the graft.
- Phase III (3-5 months): Running progression once quad strength reaches 70-80% and single-leg squat is pain-free.
- Phase IV (6-9+ months): Plyometrics and cutting; return-to-sport requires a limb symmetry index (LSI) >90% on strength and hop testing.
Meniscus Repair vs Meniscectomy
A high-yield distinction because the two procedures have opposite early weight-bearing rules.
| Procedure | Weight-Bearing | ROM | Return-to-Activity |
|---|---|---|---|
| Partial meniscectomy | WBAT immediately | Full as tolerated | 4-6 weeks |
| Meniscus repair | NWB or TTWB 4-6 weeks; brace limits flexion (often 0-90 degrees) | Progress flexion gradually; avoid deep loaded flexion ~4 months | 4-6 months |
Ankle and Foot
Lateral Ankle Sprain Grading
| Grade | Tissue State | Weight-Bearing | Typical PTA Program |
|---|---|---|---|
| I | Stretched ligament, no laxity | FWB with mild support | Ice, compression, early ROM, isometrics |
| II | Partial tear, mild laxity | PWB with brace 1-2 weeks | Progressive ROM, proprioception, peroneal strengthening |
| III | Complete tear, gross laxity | Immobilize 2-4 weeks | Slow loading, brace, balance progression, sport drills |
The anterior talofibular ligament (ATFL) is the most commonly injured, usually from inversion plantarflexion. Proprioceptive retraining (single-leg balance, wobble board) is essential to prevent chronic instability.
Plantar Fasciitis
Morning heel pain with first steps and after rest. PTA care: plantar fascia and gastrocnemius-soleus stretching, eccentric heel drops, ice massage with a frozen bottle, night splints, low-Dye taping, and footwear education.
Achilles Tendon Repair
Accelerated functional rehab favors early protected weight-bearing in a controlled ankle motion (CAM) boot with heel wedges weaned over 6-8 weeks. The PTA progresses AROM, isometrics, then concentric and finally eccentric loading; running typically resumes 4-6 months post-op. Avoid passive dorsiflexion past neutral early, which stresses the repair.
PTA Decision-Making and Common Traps
Lower-extremity post-op items reward the PTA who reads the weight-bearing order and the surgical procedure together, then chooses the intervention that respects both. Three distinctions account for most missed questions.
Repair vs Resection Logic
Whenever tissue is repaired (meniscus repair, ACL reconstruction, Achilles repair), early loading is protected to allow healing. Whenever tissue is resected or smoothed (partial meniscectomy, debridement), early loading is usually permitted because nothing must heal under tension. Apply the same logic to bone: a stable, surgically fixed fracture often allows earlier loading than a fracture managed by closed reduction in a cast.
Extension Is King at the Knee
After TKA or ACL-R, losing terminal extension is more disabling than losing a few degrees of flexion, because a flexion contracture forces a flexed-knee gait, increases quad demand, and raises fall risk. The PTA prioritizes full extension early (prone hangs, heel props, terminal knee extension) and reports any persistent extension lag.
When to Modify vs When to Call the PT
| Situation | PTA Action |
|---|---|
| Mild post-session soreness resolving in <24 h | Continue program; document |
| Effusion or pain persisting >24 h after a session | Reduce dosage within the POC; document and inform PT |
| Patient requests to advance past a written phase criterion | Continue current phase; communicate request to PT |
| New calf pain, warmth, and swelling (possible deep vein thrombosis) | Stop activity; notify PT and physician immediately |
| Weight-bearing status unclear or contradicts the order | Clarify with PT before ambulating |
A deep vein thrombosis (DVT) is the highest-stakes red flag in LE post-op rehab: unilateral calf pain, warmth, swelling, and tenderness warrant stopping activity and immediate escalation rather than continued exercise or stretching, which could dislodge a clot. The PTA's authority to modify dosage never extends to overriding a weight-bearing precaution or a surgeon-set ROM limit.
A patient is 3 days post posterior total hip arthroplasty (THA) and asks the PTA for help putting on socks while sitting on the edge of the bed. Which PTA action BEST protects the surgical hip?
Two patients are on the PTA's caseload after knee surgery yesterday: Patient A had a partial medial meniscectomy and Patient B had a medial meniscus repair. Both ask to ambulate to the bathroom. What is the MOST appropriate PTA response based on standard protocols?