Low-load exercises with concurrent blood flow restriction as rehabilitation for unspecific knee pain to a former American football player: A case report

Introduction

Anterior knee pain is not a well-defined condition due to the variety of symptoms, pain location and pain level experienced by the patient. Underlying factors could be patella abnormalities, muscular imbalances or weakness leading to patella malalignment on flexion and extension. ¹ Progressive resistance training (PRT) of quadriceps is recommended ² ; however, due to knee pain and joint swelling, PRT may be contraindicated. The feasibility of low-load exercises with concurrent blood flow restriction (LL-BFR) has previously been tested in patients with severe knee osteoarthritis, ³ with reactive knee arthritis ⁴ and with malleolus fracture. ⁵ LL-BFR was found to be a safe and well-accepted exercise modality that patients can administer with minimal supervision and induce gains in muscle strength and size comparable to that of conventional PRT. ⁶ The purpose of this case report is to describe the outcome of 12 weeks of LL-BFR as a rehabilitation method for anterior knee pain.

Case description

The case concerns a former male American football player, 30 years of age, from Denmark, now employed as a health care researcher. He has no prior medical or psychosocial history, and roughly adhering to the Danish Health Authority recommendation for diet and physical activity. He performed 12 repetitions (reps) of goblet squats with a 24 kg kettlebell with a maximal degree of knee flexion and felt pain in the left knee. This incident provoked several months of moderate pain levels, which was exacerbated by the usual heavy slow resistance training. Ultimately, the patient was unable to continue his usual high-loading exercise routine. Daily life activities such as negotiating stairs and lifting heavy objects were moderately painful. Magnetic resonance imaging showed normal meniscus and cruciate ligaments and no extra joint fluid. The patient was examined by a physiotherapist and introduced to 12 weeks of LL-BFR as knee rehabilitation after which he was followed up by the same physiotherapist. The patient accepted to engage in the study and signed a written informed consent in accordance with the Helsinki Declaration. According to Danish law, case studies do not require formal ethical approval. This manuscript was written in accordance with the CARE guidelines. ⁷

Low-load blood flow restriction training

The patient was instructed to perform three LL-BFR exercises three times per week; goblet squats, single-leg knee extensions and single-leg knee flexions for the affected and non-affected limb. A conically shaped pneumatic cuff (Occlude APS Aarhus, Denmark; size: large, width = 11.7 cm) was applied at the most proximal part of the exercising limb and inflated to 80% of the pressure required for complete restriction of the blood flow into the limb, measured seated on an examination table with ultrasound Doppler. ³ The patient was taught to correctly apply the cuff and regulate cuff pressure to ensure consistent inflation during the exercises. Exercises were performed in four sets with 30 reps in set 1, 15 reps in set 2–3, and to volitional in set 4 and 30 s rest between sets and 2–5 min rest between exercises ⁸ (Table 1). When more than 15 reps were achieved in set 4, the exercise load was increased with the smallest increment possible, that is, 2 kg for the goblet squat and 5 kg for the single-leg knee extensions and flexions. Load and reps were matched for the non-affected limb. The cuff was deflated immediately after the last set of each exercise. A physiotherapist instructed the patient to perform the exercises at baseline and again after 6 weeks of exercise. The patient completed all planned LL-BFR sessions.

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Table 1.

Exercise variables.

Exercise variable
Blood flow restriction	80% LOP
Cuff width	11.7 cm
Sets	4
Load intensity	30% 1 RM
Repetitions first set	30
Repetitions second, third and fourth set	15
Contraction modes per repetition	2 s concentric phase; 0 s isometric phase; 2 s eccentric phase
Range of motion	Maximum
Rest between sets	30 s
Rest between exercises	5 min
Rest between sessions	>24 h

LOP: limb occlusion pressure; RM: repetition maximum.

Outcome measures

Maximal voluntary isometric contraction (MVIC) of the patient’s quadriceps was assessed using an isometric dynamometer (Humac Norm, CSMI, Stoughton, MA). The patient was seated with the hip flexed to approximately 90°. MVICs were performed at 70°, and the trial with the highest MVIC value was used to determine the patient’s MVIC. The patient was instructed to perform the MVIC as rapidly and forcefully as possible, sustaining maximal force exertion for approximately 3 s, with 90 s of rest between each trial. Real-time visual feedback and strong verbal support were provided to the patient during the test. Single-legged hop test, ⁹ low-thigh circumference 10 cm above apex patella, the Knee Injury and Osteoarthritis Outcome Score (KOOS) ¹⁰ and the Forgotten Knee Joint Score (FJS) ¹¹ was assessed at baseline and after 12 weeks of LL-BFR (Table 2).

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Table 2.

Outcome measures from baseline to 12 weeks of low-load resistance training with concurrent blood flow restriction.

Outcome measure		Baseline	12 weeks	Absolute difference	% Change
Maximal isometric voluntary contraction (Nm/kg)	Right	3.5	3.7	0.2	6
	Left	3.1	3.5	0.4	13
Single-leg hop test (cm)	Right	143	146	3	2
	Left	115	141	26	23
Low-thigh circumference (cm)	Right	49.4	51.8	2.4	5
	Left	59.6	51.1	1.5	3
KOOS (points)
Pain		69.4	80.6	11.2	16
Symptoms		92.9	96.4	3.6	4
ADL		97.1	94.1	−3	−3
Sport and Recreation		80.0	65.0	−15.0	−19
Quality of life		43.8	50.0	6.3	14
FJS		27.1	66.7	69.6	146

KOOS: Knee Osteoarthritis Outcome Score; ADL: activities of daily living; FJS: Forgotten Knee Joint Score; Nm: Newton meter; kg: kilogram; cm: centimeter.

Results

The patient completed all planned exercise sessions. Total weight added to the exercises for the affected leg at the end of the intervention period equated to 20 kg. MVIC of knee extension improved from 286 to 326 Nm (14%) on the left limb, and from 328 to 350 Nm (7%) on the right limb. Single-legged hop test improved with 26 cm (23%) on the left limb and 3 cm (2%) on the right limb (Table 2). Thigh circumference increased 1.5 cm on the left limb and 2.4 on the right limb. KOOS pain, KOOS quality of life and FJS demonstrated improvements of 11, 6 and 40 points, respectively. After the LL-BFR rehabilitation, the patient was able to return to his usual lower-limb training regime consisting of traditional heavy-load exercises (i.e. barbell squats, deadlifts, lunges).

Discussion

To our best knowledge, this is the first report of unsupervised LL-BFR provided to a patient suffering from patellofemoral pain. Thus, our case report extends our understanding about the applicability of home-based LL-BFR as a viable and safe rehabilitation strategy in patients suffering from patellofemoral, similar to that of heavy-load resistance training.^12,13 Interestingly, Giles et al. observed that patients who experience pain with quadriceps contractions (i.e. during knee extensions) induced significantly greater improvements in knee extensor torque after completing 8 weeks of LL-BFR leg press and knee extension compared to the same protocol with heavy loads. Thus, when pain is attenuating the load used during heavy-load resistance training, LL-BFR is more effective in terms of gains in maximal muscle strength and size.

The patient in our case report demonstrated excellent exercise adherence with no adverse events. This is in line with our previous studies where unsupervised LL-BFR has been suggested to be safe and feasible in various patient populations.^4–6,14

Knee extensor MVIC increased 14% in the affected lower limb following the intervention. In contrast, no-to-minor improvements were observed in the non-affected lower limb. Thus, matching the workload to that of the affected limb may not have yielded a sufficient stimulus to promote gains in maximal muscle strength. The gains in knee extensor MVIC strength in the affected lower limb are lower than the improvements reported in Giles et al. ¹² and Constantinou et al. ¹³ who both found that LL-BFR and conventional PRT improved knee extensor MVIC in patients with patellofemoral pain. This may be due to differences in the exercise protocols and the relatively high baseline fitness level of our patient.

The patient demonstrated a 23% improvement in single-legged hop test for the affected limb and no improvement in the non-affected limb, reducing the between-limb asymmetry from −28 cm at baseline to −5 cm at follow-up. Hence, as with knee extensor MVIC, the lack of improvements for the non-affected limb may reflect an insufficient exercise load to improve jumping performance.

Thigh circumference 10 cm above the apex patella was observed to increase more on the non-affected limb. However, the test-retest variability in mid-thigh circumference has been reported to be −0.3 ± 0.5. ¹⁵ Therefore, it may be difficult to determine if the between-limb differences in thigh circumference are due to measuring error. Nonetheless, both thighs appear to have increased the circumference following the intervention.

The patient demonstrated clinically meaningful changes in KOOS pain and FJS. That is, a 10-point change for the KOOS subscales is considered to be a clinically relevant change. A 40-point change in FJS was observed, which is higher than the change observed in a previous case report of a patient suffering from reactive arthritis who performed 12 weeks of home-based unsupervised LL-BFR. ⁴ Ultimately, this indicates that the patient benefited from the LL-BFR protocol.

Conclusion

The present case study indicates that even with low amounts of supervision, LL-BFR may increase muscle strength, functional performance and improve key patient-reported outcomes. LL-BFR seems to be a promising low-load exercise method to help patients back to a healthy lifestyle of training and being physically active.