Back Pain, Hip And Knee Injuries
Lumbar back pain is a common presentation to the Emergency Department, and can be very challenging to manage. Patients may arrive at the Emergency Department with an agenda that includes hospital admission for analgesia and rehabilitation. This is not practical or desirable: after exclusion of significant pathology, early mobilisation is the most effective treatment. Back pain may also be caused by hip disease and retroperitoneal organs, e.g. aorta, pancreas.
There are four conditions that must not be missed.
1. Abdominal aortic aneurysm (Chapter 19).
3. Epidural abscess or haematoma.
4. Large prolapsed disc causing neurological deficit or cauda equina syndrome.
Therefore any history and examination must document the following.
• Age, back pain history, history of malignancy.
• Pain at rest, pain wakes at night.
• History of trauma, fever, intravenous drug use, anticoagulation.
• Straight leg raising, angle, crossed leg raise.
• Power at each joint (flexion, extension).
• Reflexes: knee, ankle, plantar.
• Incontinence, perineal anaesthesia, reduced anal tone (implies possible cauda equina syndrome).
Crossed straight leg raising: lifting the unaffected leg reproduces pain in the other leg. This is a very sensitive indicator of nerve root irritation, e.g. from a prolapsed disc.
If there are no abnormalities and the patient is otherwise well, the diagnosis is likely to be mechanical back pain.
Investigations are rarely necessary if no red flag symptoms. MRI is the gold standard for investigating spinal neurological problems. Urgent MRI scanning is indicated if cauda equina is suspected. Lumbar spine X-ray (70 CXR) is only indicated with a history of trauma or if malignancy is suspected.
A positive but firm attitude to encourage mobilisation may be necessary: Emergency Department nursing staff are particularly skilled at this.
The combination of an NSAID (e.g. ketorolac) and paraceta- mol/codeine-based analgesia is a good starting point. Diazepam acts as a muscle relaxant if there is significant spasm, but should only be given for a couple of days.
Hip and knee injury
The hip is an inherently stable joint, which requires substantial energy to disrupt. The knee’s stability depends on muscles, tendons, ligaments and cartilage, all of which are vulnerable to injury. Osteoporotic bone is vulnerable to low-energy injuries, i.e. ‘fragility fractures’ such as fractured neck of femur (#NoF).
Look Assess gait and inspect for joint swelling or asymmetry. Look for shortening and external rotation (#NoF) or flexion and internal rotation (dislocation of hip). Swelling of the knee joint may be due to a joint effusion. Acute traumatic effusion occurs as a result of bleeding from bony or ligamentous injury.
Feel Areas of tenderness may indicate fracture, e.g. patella, head of fibula. Knee effusion is detected by pushing the patella down so it makes contact with the anterior surface of the femoral condyle – ‘patellar tap’.
Move Assess all hip movements. Internal/external rotation at the hip is a sensitive test for fractures. Assess range of movement of knee, specifically for pain or instability (ligament injury) or locking/ unlocking (meniscus tear/loose body).
• Knee ligamentous stability: ACL, PCL, LCL, MCL (anterior and posterior cruciate, lateral and medial collateral ligaments).
• Knee meniscal stability: Apley’s test.
• Patellar stability: apprehension test.
Knee dislocation damages the popliteal artery, which always needs expert vascular assessment. The common peroneal nerve is at risk in lateral knee injuries: test for dorsiflexion of foot and sensation over dorsum of foot.
• Blood glucose, urine dipstick, ECG in patients with falls.
• FBC and group and save indicated in all patients with pelvic or femur fractures, as bleeding is often underestimated.
• In frail elderly patients, even low amounts of energy can cause fractures. All possible hip fractures should have an X-ray of the pelvis and lateral hip. The pelvis and pubic rami are brittle ring structures, and like a ‘Polo’ ® mint, they can never be broken in one place only.
• The Ottawa knee rules prevent unnecessary knee X-rays.
• CT is useful for pelvic and tibial plateau fractures.
• MRI is the gold standard for the diagnosis of knee injuries and occult hip fractures.
Lower limb fractures are painful. Intravenous opiates are often necessary. A femoral nerve block gives effective analgesia for femoral fractures at/below the trochanter. Femoral shaft fracture requires a traction splint.
A tense, painful knee haemoarthosis should be aspirated. This also allows examination of cruciate function, reduces intra-articular adhesions, or confirms haemarthrosis vs. blood-stained effusion. By putting the aspirate into a bowl, fat globules floating on the surface will be seen if there is a fracture.
Most patients with isolated knee injuries will be able to go home in a knee brace or a Robert Jones bandage (a wool and crepe bandage built up to support the extended knee) with outpatient clinic follow-up.
Hip and femur
Fractured neck of femur is common in the elderly and requires operative fixation. Consider possible causes for falling (Chapter 29).
A patient who has a clinically suspected fractured neck of femur but normal X-rays needs admission and further investigation. These patients often have fractured pubic rami, or impacted fractures seen on further imaging, e.g. MR.