Differential diagnosis of joint pain includes the following:
- Patellar fractures
- Supracondylar fractures of femur
- Tibial fractures involving the joint
- Medial and lateral collateral ligament damage
- Cruciate ligament damage
- Rupture of quadriceps tendon
- Rupture of the patellar tendon
- Mensical tears
- Pyogenic arthritis
- Rheumatoid arthritis
- Reactive/Reiter’s syndrome
- Ankylosing spondylitis
- Charcot’s joint
- Disorders of alignment:
- Genu varum (bow legs)
- Genu valgum (Knock knee)
- Patellofemoral instability
- Referred pain from the hip/back
With fractures there will usually be an obvious history of trauma.
Usually blood borne. More common is children. May occur in adults on steroids or who are immunosuppressed. The patient presents with a hot, painful, tender joint with malaise and fever.
In rheumatoid arthritis the patient complains pain, swelling and stiffness. Symptoms of rheumatoid arthritis may be present elsewhere.
Osteoarthritis is common in the knee. The patient may be overweight and elderly. There is pain on movement, stiffness and deformity.
Gout may present with pain and swelling of the knee. Pseudogout (pyrophosphate deposition disease) may also present in the knee joint.
The lower end of the femur and the upper end of the tibia are common sites of osteogenic sarcoma.
Bursitis presents with swelling either in front or behind the knee. The swelling may be painless. A bursa may become infected, in which case the patient will present with a tender, red, hot swelling.
Disorder of alignment
With genu varum the patient presents with bow legs. In children, this is usually associated with a disorder of growth, often with a bony injury to the area of epiphyses. In genu valgum (knock knee), the patient is often a child who has flat feet.
Dislocation of the patella may occur. In the acute form there may be a history of a blow.
It is very common for pain to be referred from the hip or the back.
Fractures will usually be obvious. There will be pain, tenderness, deformity and crepitus.
The patient will be febrile with a hot, red, tender, painful, swollen joint.
With rheumatoid arthritis there will be fever, pain and swelling with decreased range of movement and synovial thickening.
With osteoarthritis there will be swelling due to osteophyates, and possibly thickened synovium or effusion.
With gout the joint is red, hot and swollen and there is limitation of movement. A similar appearance occurs in Pseudogout.
The joint will be grossly swollen and deformed. There will be abnormal mobility which is painless. Test for abnormality of dorsal column sensation (joint position sense).
● FBC, ESR
● Rheumatoid factor/anti-CCP antibodies: Rheumatoid arthritis
● Serum uric acid: gout
● Knee X-ray (AP, lateral, tunnel and skyline views)
● CXR:Secondary deposits in osteogenic sarcoma
● Blood culture: Pyogenic arthritis
● Joint aspiration: Gram stain and culture and sensitivity-infection
● Isotope scan: Tumour, infections
● MRI: Ligamentous injuries, e.g. cruciates. Avascular necrosis synovitis.
● Synovial biopsy: Confirmation of diagnosis