Execution
- 1Ask whether the mechanism involved valgus force or lateral blow to the knee.
- 2Palpate the medial joint line and MCL course for focal tenderness.
- 3Perform valgus stress at 30 degrees knee flexion.
- 4Repeat valgus stress at 0 degrees to screen for combined injury.
- 5Interpret MCL likelihood using mechanism, tenderness, laxity, pain, and end feel together.
Positive outcome
A positive cluster is supported by valgus injury mechanism, medial tenderness, and pain or laxity with valgus stress at 30 degrees. Laxity only at 30 degrees suggests isolated MCL injury, while laxity at 0 degrees suggests combined ligament or capsular injury. The cluster is a clinical reasoning framework rather than one validated named rule.
Studies
| Study | Reliability | Sn | Sp | LR+ | LR− |
|---|---|---|---|---|---|
| Kastelein et al. (2008) | prospective cohort, n=134, primary care, MRI reference | 56 | 91 | 6.4 | 0.5 |
| Kastelein et al. (2008) — Pain valgus stress 30° alone | NA | 78 | 67 | 2.3 | 0.3 |
| Kastelein et al. (2008) — Laxity valgus stress 30° alone | NA | 91 | 49 | 1.8 | 0.2 |
CommentMCL diagnosis is strongest when mechanism, local tenderness, and valgus laxity agree. Kastelein 2008 found that combining at least 1 of 2 history determinants (external valgus force, rotational trauma) with positive pain AND laxity on valgus stress at 30° gave LR+ 6.4 (clinically meaningful), with PVP up to 63%. The exact named cluster is less standardized than ACL or PFPS rules. I kept value moderate because combined findings are clinically stronger than isolated tenderness or pain.
Moderate Clinical Value