9.5 Musculoskeletal Soft Tissue Injuries, Back Pain, & Physical Medicine

Triage of Low Back Pain & Red Flag Identification

Low back pain (LBP) is one of the most frequent reasons for primary care visits. Clinical evaluation centers on triaging patients into three broad categories: non-specific mechanical back pain ($~90%$), radiculopathy / spinal stenosis ($5\text{--}8%$), and serious underlying pathology ($<1\text{--}2%$).

Red Flags for Serious Underlying Pathology (TUNA FISH Mnemonic)

• Trauma: Significant mechanism of injury or minor fall in an osteoporotic/elderly patient.
• Unexplained Weight Loss: Suspicion of spinal metastasis.
• Neurologic Deficit: Progressive motor weakness, cauda equina symptoms.
• Age: $<20$ or $>50$ years at initial presentation.
• Fever, Chills, Night Sweats: Spinal infection (epidural abscess, osteomyelitis, discitis).
• IV Drug Use / Immunosuppression: High risk of spinal infection.
• Steroid Use (Chronic): High risk of vertebral compression fracture.
• History of Malignancy: Metastatic disease (Prostate, Breast, Renal, Thyroid, Lung — "PB-RTL").

Cauda Equina Syndrome: Emergency Protocol

Cauda equina syndrome results from massive central compression of the lumbosacral nerve roots below the conus medullaris (most commonly due to a large central L4/L5 or L5/S1 disc herniation).

• Clinical Triad:
  1. Saddle Anesthesia: Sensory loss over the perineum, buttocks, and inner thighs (S3–S5 dermatomes).
  2. Bowel and Bladder Dysfunction: Urinary retention with overflow incontinence (most sensitive indicator), or fecal incontinence.
  3. Bilateral Lower Extremity Deficits: Progressive bilateral motor weakness and loss of anal sphincter tone on digital rectal exam.
• Mandatory Emergency Action: Order a STAT emergency non-contrast MRI of the lumbosacral spine and obtain immediate emergency spine surgery consultation (Neurosurgery or Orthopedics) for urgent decompressive laminectomy (ideally within 24 to 48 hours of symptom onset to prevent permanent paralysis and incontinence).

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Lumbar Radiculopathy & Spinal Stenosis

Lumbar Radiculopathy

Radiculopathy involves nerve root impingement secondary to herniated nucleus pulposus or osteophytic nerve entrapment. Physical exam features a positive Straight Leg Raise (SLR) test (reproduction of radicular pain down the leg when passive elevation reaches 30–70 degrees).

Management Rules for Uncomplicated Radiculopathy

• $>80%$ of acute lumbar disc herniations resolve spontaneously with conservative care.
• First 4 to 6 Weeks: Conservative management with NSAIDs, short-term activity modification, and continuation of light daily activities. Prolonged bed rest is strictly contraindicated.
• Imaging Rule: Routine X-rays or MRI are NOT indicated in the first 4 to 6 weeks unless red flags or severe progressive motor deficits are present.

Lumbar Spinal Stenosis

• Pathophysiology: Hypertrophy of ligamentum flavum, facet joint osteoarthritis, and disc degeneration narrowing the spinal canal in elderly patients ($>60$ years).
• Clinical Feature: Neurogenic Claudication — bilateral leg pain, aching, heaviness, or numbness induced by walking or standing upright, and relieved by spinal flexion ("shopping cart sign" — leaning forward opens the spinal canal diameter).
• Differentiating Claudication: Vascular claudication is brought on by exertion, relieved immediately by standing still without flexing, and associated with diminished peripheral pulses.

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Soft Tissue Shoulder, Knee, & Ankle Pathology

Shoulder Rotator Cuff & Impingement

• Rotator Cuff Muscles (SITS):
  • Supraspinatus: Initial 15 degrees shoulder abduction; tested via Empty Can (Jobe) test.
  • Infraspinatus & Teres Minor: External rotation; tested via resisted external rotation.
  • Subscapularis: Internal rotation; tested via Lift-off test or Belly-press test.
• Subacromial Impingement: Positive Neer and Hawkins-Kennedy signs.
• Full-Thickness Tear: Positive Drop Arm test. Acute traumatic tears in young patients warrant early surgical repair, whereas chronic tears in older adults are managed conservatively with physiotherapy and subacromial corticosteroid injections.

Knee Soft Tissue Pathology & Ottawa Knee Rules

• Anterior Cruciate Ligament (ACL) Tear: Non-contact pivot/deceleration injury with a loud "pop" followed by immediate joint effusion (hemarthrosis). Positive Lachman test (most sensitive) and Anterior Drawer test.
• Meniscal Tears: Twisting injury on flexed knee, catching/locking sensation, and joint line tenderness. Positive McMurray test.
• Ottawa Knee Rules: Radiographs of the knee are indicated ONLY if an acute knee injury is present plus $\ge 1$ of the following:
  1. Age $\ge 55$ years.
  2. Isolated bone tenderness of the patella.
  3. Tenderness at the head of the fibula.
  4. Inability to flex the knee to 90 degrees.
  5. Inability to bear weight both immediately after injury and in the emergency department for 4 steps.

Ankle Sprain & Ottawa Ankle Rules

Inversion ankle sprains most commonly injure the Anterior Talofibular Ligament (ATFL).

[Ottawa Ankle Rules: Obtain Ankle X-Ray Series IF Pain in Malleolar Zone AND ANY OF:]
  ├─ Bone tenderness along distal 6 cm of posterior edge or tip of Lateral Malleolus
  ├─ Bone tenderness along distal 6 cm of posterior edge or tip of Medial Malleolus
  └─ Inability to bear weight both immediately after injury and in ED for 4 steps

[Ottawa Foot Rules: Obtain Foot X-Ray Series IF Pain in Midfoot Zone AND ANY OF:]
  ├─ Bone tenderness at base of 5th Metatarsal
  ├─ Bone tenderness at Navicular bone
  └─ Inability to bear weight both immediately after injury and in ED for 4 steps

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Physical Medicine & Rehabilitation (PM&R) Principles

1. Functional Restoration Focus: In chronic musculoskeletal pain, shift therapeutic goals from total pain elimination to functional restoration, active self-management, and quality of life enhancement.
2. Avoidance of Bed Rest: Bed rest beyond 24–48 hours causes severe muscle deconditioning, joint stiffness, osteopenia, and psychological dependency. Active exercise programs are superior.
3. Multidisciplinary Rehabilitation: Integrate physical therapy (core strengthening, range of motion, aerobic exercise), occupational therapy (ergonomic workplace modification), cognitive-behavioral therapy (CBT for pain coping), and non-opioid analgesics (NSAIDs, SNRIs such as Duloxetine for chronic back pain/fibromyalgia, Pregabalin for neuropathic pain). Avoid long-term opioid therapy for chronic non-cancer musculoskeletal pain.