Sinding-Larsen-Johansson Syndrome

Patients describe gradual-onset anterior knee pain localised to the inferior pole of the patella, worse with jumping, running, kicking, squatting, stair descent, and kneeling. Symptoms are aggravated by high training volumes, growth spurts, or a change in activity, and are typically intermittent over weeks to months. Usually unilateral but can be bilateral.

Examination centres on focal tenderness at the inferior pole of the patella - the cardinal sign. The proximal patellar tendon fibres may also be tender but the focal point is the inferior pole itself. Visible or palpable swelling over the inferior pole appears in more advanced cases. Pain is reproduced on resisted knee extension and on passive knee flexion at end range (stretching the extensor mechanism). Quadriceps and hamstring tightness is common. Knee range of motion is otherwise preserved with no effusion and normal neurovascular examination. In atypical or unclear presentations, examine the hip - paediatric knee pain can be referred from hip pathology (Perthes, SUFE).

Differentials: Osgood-Schlatter (tibial tubercle tenderness), patellar tendinopathy in skeletally mature athletes (jumper's knee, same region but in a mature tendon), patellofemoral pain syndrome, bipartite patella (typically superolateral pole), OCD of the knee (posterior medial femoral condyle tenderness, mechanical symptoms), patellar sleeve avulsion (see red flags), and juvenile idiopathic arthritis (effusion, morning stiffness, constitutional features).

SLJ is primarily a clinical diagnosis. Imaging is used to exclude alternative pathology and, critically, to rule out patellar sleeve avulsion in acute presentations.

Plain radiographs (AP, lateral, and skyline views) show irregularity, fragmentation, or calcification at the inferior pole of the patella. Findings can be subtle and similar appearances occur in asymptomatic children, so interpret alongside clinical findings - supportive, not standalone diagnostic. Any bony fragment at or near the inferior pole in an acute presentation, with or without patella alta, mandates urgent orthopaedic assessment for patellar sleeve avulsion.

Point-of-care ultrasound is a useful radiation-free confirmatory tool in SEM/MSK practice. It demonstrates inferior pole fragmentation, thickening of the proximal patellar tendon, and local hypervascularity on power Doppler. Particularly valuable in paediatric populations where radiation avoidance matters.

MRI is not routinely required for SLJ. Use it if the diagnosis is uncertain, symptoms do not settle, or patellar sleeve avulsion or OCD is suspected. MRI shows bony oedema, cartilage integrity, and can identify cartilaginous sleeve injury. Inflammatory markers and routine bloods are not indicated unless JIA, infection, or malignancy is part of the differential.

UK practice for SLJ aligns with BSCOS and paediatric sports medicine consensus. The cornerstones are reassurance, activity modification, and symptom-guided return to sport. SLJ is typically self-limiting and resolves with skeletal maturity.

Conservative management is usually sufficient: reassurance about the traction-apophysitis mechanism and its self-limiting course, activity modification (reduce rather than eliminate aggravating activities, tailored to symptom severity - total cessation of sport is rarely necessary), ice after activity, and simple analgesia. Paracetamol is first-line, with short courses of NSAIDs (oral or topical) per NICE CKS when needed; routine long-term NSAIDs are not appropriate. A patellar tendon strap or infrapatellar brace is an optional symptomatic adjunct with limited evidence. Education of parents, coaches, and schools about the self-limiting nature and training load is important.

Not recommended: prolonged immobilisation or casting (causes deconditioning without benefit), corticosteroid injection (avoid in the skeletally immature extensor apparatus), and routine imaging in a clinically typical presentation.

Referral: paediatric orthopaedics or paediatric SEM for atypical features, persistent symptoms beyond skeletal maturity, diagnostic uncertainty, or significant functional limitation. Urgent orthopaedic assessment for any suspected patellar sleeve avulsion.

Prognosis is excellent: symptoms resolve as the inferior pole ossification centre fuses with skeletal maturity. Residual asymptomatic imaging irregularity may persist into adulthood without functional consequence.

Rehabilitation is symptom-guided with no fixed protocol. The principles are to maintain conditioning while symptoms settle, then progressively reload.

Relative rest modifies (rather than eliminates) jumping, sprinting, and deep knee flexion loading during symptomatic periods. Quadriceps and hamstring stretching addresses the tight chain driving traction forces, particularly during growth spurts. Progressive quadriceps strengthening with closed-chain exercises and eccentric control (decline squats introduced cautiously as symptoms allow) is the loading cornerstone. Gluteal and core strengthening optimise lower-limb alignment and offload the extensor mechanism. Biomechanical review covers landing mechanics, running technique, footwear, and orthotic assessment.

Return to sport is graduated and symptom-guided with no rigid calendar. Return criteria: pain-free full squat, pain-free single-leg jumping, symmetric strength, and sport-specific drill completion. Training-load management addresses the workload spike that often precedes presentation. Educate the athlete and parents about recurrence risk during growth spurts.

• •BSCOS paediatric sports medicine pathways - reassurance, activity modification, and symptom-guided return to sport are first-line; corticosteroid injection should be avoided in the skeletally immature extensor apparatus.
• •BJSM review on apophyseal injuries in young athletes - traction apophysitis is self-limiting; conservative management with load modification is the standard.
• •NICE CKS Knee pain (assessment) - guides initial assessment in primary care and flags red-flag triggers for atypical presentations.
• •Iwamoto et al. (2009, J Orthop Sci) - SLJ resolves with skeletal maturity in the majority of cases; residual radiographic irregularity does not predict ongoing symptoms.
• •Maffulli et al. (2003) - Patellar sleeve avulsion is the critical differential: a small ossific fragment may be the only X-ray clue to a much larger cartilaginous sleeve injury disrupting the extensor mechanism.

• •SLJ = traction apophysitis of the INFERIOR pole of the patella in the skeletally immature; tenderness at the inferior pole is the cardinal sign.
• •SLJ (10-13 years) presents slightly younger than Osgood-Schlatter (12-15) because the inferior patellar pole ossifies earlier than the tibial tubercle.
• •Patellar sleeve avulsion is the critical do-not-miss: acute onset, inability to straight-leg raise, patella alta, with or without a subtle bony fragment on X-ray - urgent orthopaedic assessment.
• •Imaging is not routinely required in typical presentations; POCUS is a useful radiation-free adjunct in paediatric SEM practice.
• •Corticosteroid injection should be avoided in the skeletally immature extensor mechanism.
• •Same anatomical axis as patellar tendinopathy and Osgood-Schlatter - skeletal maturity drives the diagnosis at each point on the patella-tendon-tibial-tubercle line.