Quadriceps Spasticity: An Overlooked Cause of Knee Pain

Introduction: Published by By Dr Ali Musa HCPC MSc Physiotherapist MY Sports Injury Manchester

Knee pain is one of the most common musculoskeletal complaints seen in physiotherapy practice. It is frequently attributed to arthritis, cartilage damage, or meniscal injuries, yet many people present with disabling pain despite relatively normal imaging. One overlooked mechanism is quadriceps spasticity, where one or more of the four quadriceps muscles dominate and disrupt patellofemoral mechanics.

The quadriceps consist of the vastus medialis, vastus lateralis, rectus femoris, and vastus intermedius. Each can create a distinct pain pattern when spastic, and recognising these patterns can transform clinical reasoning and treatment.

Pain Patterns and the Quadriceps Complex

1. Vastus Medialis (VMO)
   • Over-activity of the VMO produces medial knee pain, often mistaken for meniscal or MCL pathology.
   • Delayed or uncoordinated VMO activation relative to VL is well documented in patellofemoral pain syndrome (PFPS) (Chester et al., 2008; Cowan et al., 2001).
2. Vastus Lateralis (VL)
   • Spasticity pulls the patella laterally, creating outer knee pain and sometimes mimicking IT band syndrome.
   • Maltracking from VL dominance is a recognised mechanism in PFPS (Waryasz & McDermott, 2008).
3. Rectus Femoris
   • As a biarticular muscle, rectus femoris spasticity typically causes anterior knee pain, especially during squats, stair climbing, or running.
   • Tightness of rectus femoris has been shown to correlate with anterior knee pain (Ali et al., 2023).
4. Vastus Intermedius
   • Hidden beneath the others, spasticity here can create deep, retro-patellar pain described as “grinding” or “pressure.”
   • While harder to isolate clinically, imaging studies confirm its fibre orientation allows it to increase compressive forces across the patella (El Sawy et al., 2021).

Why Spasticity Leads to Pain

Spasticity changes the timing, load distribution, and stiffness of the quadriceps. When one head dominates, the patella is pulled unevenly, creating abnormal compressive forces. Over time, this irritates cartilage, tendons, and subchondral bone — even in the absence of structural injury.

• Studies confirm quadriceps tightness and imbalance increase patellofemoral stress and pain (Waryasz & McDermott, 2008; Garza-Borjón et al., 2024).
• Delayed VMO activation is associated with altered patellar tracking (Cowan et al., 2001).
• Quadriceps atrophy and inhibition are frequently observed in patients with patellofemoral pain (Giles et al., 2013).

Clinical Example

A 62-year-old patient presented with medial knee pain, convinced she had a meniscus tear. Imaging was unremarkable. On assessment, her vastus medialis was markedly spastic. After targeted manual release, activation retraining, and progressive strengthening, her symptoms reduced dramatically and she returned to walking without pain.

This mirrors research showing that targeted quadriceps retraining improves pain and function in PFPS (Bhatt et al., 2015).

Management Approach

Effective treatment involves a combination of:

• Manual release to reduce spasticity and restore muscle length.
• Neuromuscular re-education to balance activation (e.g., retraining VMO timing relative to VL).
• Progressive strengthening of all quadriceps, ensuring symmetry of load.
• Education to reassure patients that knee pain often stems from functional imbalance rather than irreversible “wear and tear.”

Conclusion

Knee pain is not always structural. Quadriceps spasticity can drive highly specific pain patterns depending on which head is affected. By identifying and addressing these imbalances, clinicians can offer targeted treatment that relieves pain and restores function — often in cases where scans show little and patients have lost hope.

Physiotherapy has the potential to deliver permanent, life-changing outcomes when we move beyond the joint itself and consider the deeper muscular mechanisms at play. Book With Dr Ali Musa HCPC physiotherapist to get a full medical assessment & Treatment plan with recommendations.

References (selected)

• Chester R, et al. BMC Musculoskelet Disord. 2008 – Systematic review on VMO/VL timing in PFPS.
• Cowan SM, et al. Br J Sports Med. 2001 – VMO delayed activation in patellofemoral pain.
• Waryasz GR, McDermott AY. Clin Orthop Relat Res. 2008 – Review of risk factors for PFPS including quadriceps tightness.
• Ali A, et al. J Clin Orthop Trauma. 2023 – Association between rectus femoris/gastrocnemius tightness and PFPS.
• El Sawy S, et al. Anat Cell Biol. 2021 – Morphometry of VMO.
• Giles LS, et al. J Orthop Sports Phys Ther. 2013 – Quadriceps atrophy in PFPS.
• Bhatt S, et al. Saudi J Sports Med. 2015 – Review on preferential VMO activation.
• Garza-Borjón J, et al. Orthopedic Reviews. 2024 – Pathoanatomy of patellofemoral pain.