Synopsis
Separate load-related patellofemoral pain from true lateral dislocation and structural instability, reduce acute dislocation safely, identify osteochondral injury and recurrence risk, and build exercise or surgical pathways around the actual mechanism.
- Patellofemoral pain is anterior or peripatellar load pain during squatting, stairs, running or prolonged sitting without a true dislocation history; instability produces apprehension, subluxation or a documented lateral dislocation.
- Reduce an acute lateral dislocation without delay. BOASt advises against aspirating the associated haemarthrosis routinely.
- After reduction obtain AP, lateral and skyline radiographs, document extensor and neurovascular function and inspect for osteochondral fragment or fracture.
- Do not use cast immobilisation. A pain-relief splint may permit full flexion, and unrestricted weight bearing with crutches if needed is encouraged immediately.
- Arrange age-appropriate knee-clinic assessment within 2 weeks and musculoskeletal physiotherapy within 3 weeks after first-time dislocation.
- Obtain MRI when associated osteochondral or ACL injury, haemarthrosis, locked knee, extensor failure, difficult assessment, planned surgery or failure to recover makes it relevant.
- Do not routinely stabilise an isolated first-time dislocation surgically; treat significant associated osteochondral injury and discuss any stabilisation plan in an age-appropriate MDT. Isolated lateral release is never indicated.
- For patellofemoral pain, manage training load and progressively strengthen knee and hip with movement retraining; imaging is reserved for trauma, instability, effusion, failed care or another diagnosis.
Key red flags
Failure of reduction, absent straight-leg raise, gross tibiofemoral instability or neurovascular abnormality requires urgent orthopaedic assessment and imaging beyond an isolated patellar pathway.
Large haemarthrosis, locked knee, persistent focal bony pain or visible fragment raises osteochondral fracture and supports MRI and early surgical review.
Fever, erythema and severe passive pain suggests septic arthritis rather than patellofemoral pain and requires urgent aspiration.
Recurrent dislocation in a skeletally immature person with major malalignment, severe trochlear dysplasia or syndromic laxity needs age-appropriate specialist planning.
Investigation priorities
Confirm reduction and detect fracture or osteochondral fragment.
Management branches
The patella remains laterally displaced without evidence of tibiofemoral dislocation or fracture preventing reduction.
- Provide analgesia, document neurovascular and extensor status and reduce gently without delay.
- Obtain AP, lateral and skyline radiographs and reassess straight-leg raise and osteochondral tenderness.
- Avoid routine haemarthrosis aspiration and cast immobilisation; allow weight bearing with crutches as needed.
- Arrange clinic within two weeks and physiotherapy within three, with MRI when an indicated risk or associated injury is present.